CVE-2026-42923
Degradation of service with unbounded NSEC3 hash calculations
CVE-2026-42923 is a medium vulnerability (CVSS 6.9) in Nlnet Labs Unbound, published May 20, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.34%, the 27th percentile. Fixed in unbound 1.25.2-r0.
- Severity
- 6.9 MediumCVSS 4.0, CVE List
- Exploit chance
- 0.34%EPSS, 27th percentile
- Exploitation
- None knownNot on CISA’s or ENISA’s lists
- Fixed in
1.25.2-r0unbound +105 more
Description
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Exploit likelihood
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
unboundAlpine:v3.22 | 1.19.1 up to 1.25.2-r0 | 1.25.2-r0 |
unboundAlpine:v3.23 | 1.19.1 up to 1.25.2-r0 | 1.25.2-r0 |
unboundAlpine:v3.24 | 1.19.1 up to 1.25.1-r0 | 1.25.1-r0 |
unboundAzure Linux:3 | before 1.25.1-1 | 1.25.1-1 |
python3-unboundTuxCare:AlmaLinux:9.2 From an advisory covering 2 CVEs | before 1.16.2-3.el9_2.tuxcare.els10 | 1.16.2-3.el9_2.tuxcare.els10 |
unboundTuxCare:AlmaLinux:9.2 From an advisory covering 2 CVEs | before 1.16.2-3.el9_2.tuxcare.els10 | 1.16.2-3.el9_2.tuxcare.els10 |
unbound-develTuxCare:AlmaLinux:9.2 From an advisory covering 2 CVEs | before 1.16.2-3.el9_2.tuxcare.els10 | 1.16.2-3.el9_2.tuxcare.els10 |
unbound-libsTuxCare:AlmaLinux:9.2 From an advisory covering 2 CVEs | before 1.16.2-3.el9_2.tuxcare.els10 | 1.16.2-3.el9_2.tuxcare.els10 |
python3-unboundTuxCare:AlmaLinux:9.6 From an advisory covering 3 CVEs | before 1.16.2-19.el9_6.1.tuxcare.els10 | 1.16.2-19.el9_6.1.tuxcare.els10 |
unboundTuxCare:AlmaLinux:9.6 From an advisory covering 3 CVEs | before 1.16.2-19.el9_6.1.tuxcare.els10 | 1.16.2-19.el9_6.1.tuxcare.els10 |
Show 96 moreShow less
| Package | Affected | Fixed |
|---|---|---|
unbound-develTuxCare:AlmaLinux:9.6 From an advisory covering 3 CVEs | before 1.16.2-19.el9_6.1.tuxcare.els10 | 1.16.2-19.el9_6.1.tuxcare.els10 |
unbound-dracutTuxCare:AlmaLinux:9.6 From an advisory covering 3 CVEs | before 1.16.2-19.el9_6.1.tuxcare.els10 | 1.16.2-19.el9_6.1.tuxcare.els10 |
unbound-libsTuxCare:AlmaLinux:9.6 From an advisory covering 3 CVEs | before 1.16.2-19.el9_6.1.tuxcare.els10 | 1.16.2-19.el9_6.1.tuxcare.els10 |
python3-unboundTuxCare:CentOS-Stream:8 From an advisory covering 3 CVEs | before 1.16.2-5.el8.tuxcare.els10 | 1.16.2-5.el8.tuxcare.els10 |
unboundTuxCare:CentOS-Stream:8 From an advisory covering 3 CVEs | before 1.16.2-5.el8.tuxcare.els10 | 1.16.2-5.el8.tuxcare.els10 |
unbound-develTuxCare:CentOS-Stream:8 From an advisory covering 3 CVEs | before 1.16.2-5.el8.tuxcare.els10 | 1.16.2-5.el8.tuxcare.els10 |
unbound-libsTuxCare:CentOS-Stream:8 From an advisory covering 3 CVEs | before 1.16.2-5.el8.tuxcare.els10 | 1.16.2-5.el8.tuxcare.els10 |
unboundDebian:12 | All versions, plus listed versions 1.17.1-21.17.1-2+deb12u11.17.1-2+deb12u21.17.1-2+deb12u31.17.1-2+deb12u4 Show 21 moreShow less1.17.1-2+loong641.18.0-11.18.0-21.19.1-11.19.2-11.20.0-11.21.1-11.22.0-11.22.0-21.23.1-11.24.0-11.24.0-21.24.1-11.24.1-21.24.2-11.25.0-11.25.1-11.25.2-11.26.0-11.26.0-21.26.1-1 | None known |
unboundDebian:13 | before 1.22.0-2+deb13u3, plus listed versions 1.22.0-21.22.0-2+deb13u11.22.0-2+deb13u2 | 1.22.0-2+deb13u3 |
unboundDebian:14 | before 1.25.1-1, plus listed versions 1.22.0-21.23.1-11.24.0-11.24.0-21.24.1-11.24.1-21.24.2-11.25.0-1 | 1.25.1-1 |
unboundopenEuler:22.03-LTS-SP4 From an advisory covering 5 CVEs | before 1.13.2-23.oe2203sp4 | 1.13.2-23.oe2203sp4 |
unboundopenEuler:24.03-LTS-SP1 From an advisory covering 6 CVEs | before 1.17.1-17.oe2403sp1 | 1.17.1-17.oe2403sp1 |
unboundopenEuler:24.03-LTS-SP3 From an advisory covering 6 CVEs | before 1.17.1-17.oe2403sp3 | 1.17.1-17.oe2403sp3 |
unboundopenEuler:20.03-LTS-SP4 From an advisory covering 5 CVEs | before 1.11.0-23.oe2003sp4 | 1.11.0-23.oe2003sp4 |
python3-unboundRed Hat:hummingbird:1 From an advisory covering 4 CVEs | before 0:1.25.1-1.hum1 | 0:1.25.1-1.hum1 |
unboundRed Hat:hummingbird:1 From an advisory covering 4 CVEs | before 0:1.25.1-1.hum1 | 0:1.25.1-1.hum1 |
unbound-anchorRed Hat:hummingbird:1 From an advisory covering 4 CVEs | before 0:1.25.1-1.hum1 | 0:1.25.1-1.hum1 |
unbound-develRed Hat:hummingbird:1 From an advisory covering 4 CVEs | before 0:1.25.1-1.hum1 | 0:1.25.1-1.hum1 |
unbound-dracutRed Hat:hummingbird:1 From an advisory covering 4 CVEs | before 0:1.25.1-1.hum1 | 0:1.25.1-1.hum1 |
unbound-libsRed Hat:hummingbird:1 From an advisory covering 4 CVEs | before 0:1.25.1-1.hum1 | 0:1.25.1-1.hum1 |
unbound-muninRed Hat:hummingbird:1 From an advisory covering 4 CVEs | before 0:1.25.1-1.hum1 | 0:1.25.1-1.hum1 |
unbound-utilsRed Hat:hummingbird:1 From an advisory covering 4 CVEs | before 0:1.25.1-1.hum1 | 0:1.25.1-1.hum1 |
python3-unboundRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
python3-unbound-debuginfoRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-anchor-debuginfoRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-debuginfoRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-debugsourceRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-libs-debuginfoRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-utilsRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-utils-debuginfoRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unboundRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-anchorRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-dracutRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-libsRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-develRed Hat:enterprise_linux:10.3 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
python3-unboundRed Hat:enterprise_linux:9::appstream From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
python3-unbound-debuginfoRed Hat:enterprise_linux:9::appstream From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-debuginfoRed Hat:enterprise_linux:9::appstream From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-debugsourceRed Hat:enterprise_linux:9::appstream From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-libs-debuginfoRed Hat:enterprise_linux:9::appstream From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
python3-unbound-debuginfoRed Hat:enterprise_linux:9::baseos From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unboundRed Hat:enterprise_linux:9::baseos From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-debuginfoRed Hat:enterprise_linux:9::baseos From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-debugsourceRed Hat:enterprise_linux:9::baseos From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-dracutRed Hat:enterprise_linux:9::baseos From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-libsRed Hat:enterprise_linux:9::baseos From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-libs-debuginfoRed Hat:enterprise_linux:9::baseos From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
python3-unbound-debuginfoRed Hat:enterprise_linux:9::crb From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-debuginfoRed Hat:enterprise_linux:9::crb From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-debugsourceRed Hat:enterprise_linux:9::crb From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-develRed Hat:enterprise_linux:9::crb From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-libs-debuginfoRed Hat:enterprise_linux:9::crb From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-utilsRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-anchor-debuginfoRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-libsRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-develRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-anchorRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unboundRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
python3-unboundRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-utils-debuginfoRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-debuginfoRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
python3-unbound-debuginfoRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-libs-debuginfoRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-dracutRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
unbound-debugsourceRocky Linux:10 From an advisory covering 18 CVEs | before 0:1.26.1-2.el10_3 | 0:1.26.1-2.el10_3 |
python3-unboundRocky Linux:9 From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
python3-unbound-debuginfoRocky Linux:9 From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unboundRocky Linux:9 From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-debuginfoRocky Linux:9 From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-debugsourceRocky Linux:9 From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-develRocky Linux:9 From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-dracutRocky Linux:9 From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-libsRocky Linux:9 From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unbound-libs-debuginfoRocky Linux:9 From an advisory covering 18 CVEs | before 0:1.26.1-1.el9_9 | 0:1.26.1-1.el9_9 |
unboundSUSE:Linux Enterprise Server 16.0 From an advisory covering 11 CVEs | before 1.24.1-160000.2.1 | 1.24.1-160000.2.1 |
unboundSUSE:Linux Enterprise Server for SAP applications 16.0 From an advisory covering 11 CVEs | before 1.24.1-160000.2.1 | 1.24.1-160000.2.1 |
unboundSUSE:Linux Micro 6.2 From an advisory covering 11 CVEs | before 1.24.1-160000.2.1 | 1.24.1-160000.2.1 |
unboundSUSE:Linux Enterprise Micro 5.5 From an advisory covering 11 CVEs | before 1.20.0-150100.10.25.1 | 1.20.0-150100.10.25.1 |
unboundSUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS From an advisory covering 11 CVEs | before 1.20.0-150100.10.25.1 | 1.20.0-150100.10.25.1 |
unboundSUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS From an advisory covering 11 CVEs | before 1.20.0-150100.10.25.1 | 1.20.0-150100.10.25.1 |
unboundSUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS From an advisory covering 11 CVEs | before 1.20.0-150100.10.25.1 | 1.20.0-150100.10.25.1 |
unboundSUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS From an advisory covering 11 CVEs | before 1.20.0-150100.10.25.1 | 1.20.0-150100.10.25.1 |
unboundSUSE:Linux Enterprise Server 15 SP4-LTSS From an advisory covering 11 CVEs | before 1.20.0-150100.10.25.1 | 1.20.0-150100.10.25.1 |
unboundSUSE:Linux Enterprise Server 15 SP5-LTSS From an advisory covering 11 CVEs | before 1.20.0-150100.10.25.1 | 1.20.0-150100.10.25.1 |
unboundSUSE:Linux Enterprise Server for SAP Applications 15 SP4 From an advisory covering 11 CVEs | before 1.20.0-150100.10.25.1 | 1.20.0-150100.10.25.1 |
unboundSUSE:Linux Enterprise Server for SAP Applications 15 SP5 From an advisory covering 11 CVEs | before 1.20.0-150100.10.25.1 | 1.20.0-150100.10.25.1 |
unboundUbuntu:Pro:14.04:LTS | All versions, plus listed versions 1.4.20-11.4.21-11.4.21-1ubuntu11.4.21-1ubuntu21.4.22-1ubuntu1 Show 11 moreShow less1.4.22-1ubuntu21.4.22-1ubuntu31.4.22-1ubuntu41.4.22-1ubuntu4.14.04.11.4.22-1ubuntu4.14.04.21.4.22-1ubuntu4.14.04.31.4.22-1ubuntu4.14.04.3+esm11.4.22-1ubuntu4.14.04.3+esm21.4.22-1ubuntu4.14.04.3+esm31.4.22-1ubuntu4.14.04.3+esm41.4.22-1ubuntu4.14.04.3+esm5 | None known |
unboundUbuntu:Pro:16.04:LTS | All versions, plus listed versions 1.4.22-1ubuntu61.5.7-1ubuntu11.5.7-1ubuntu21.5.8-1ubuntu11.5.8-1ubuntu1.1 Show 5 moreShow less1.5.8-1ubuntu1.1+esm11.5.8-1ubuntu1.1+esm21.5.8-1ubuntu1.1+esm31.5.8-1ubuntu1.1+esm41.5.8-1ubuntu1.1+esm5 | None known |
unboundUbuntu:Pro:18.04:LTS | All versions, plus listed versions 1.6.5-11.6.7-11.6.7-1build11.6.7-1ubuntu11.6.7-1ubuntu2 Show 11 moreShow less1.6.7-1ubuntu2.11.6.7-1ubuntu2.21.6.7-1ubuntu2.31.6.7-1ubuntu2.41.6.7-1ubuntu2.51.6.7-1ubuntu2.61.6.7-1ubuntu2.6+esm21.6.7-1ubuntu2.6+esm31.6.7-1ubuntu2.6+esm41.6.7-1ubuntu2.6+esm51.6.7-1ubuntu2.6+esm6 | None known |
unboundUbuntu:Pro:20.04:LTS | All versions, plus listed versions 1.9.0-2ubuntu11.9.0-2ubuntu21.9.4-21.9.4-2ubuntu11.9.4-2ubuntu1.1 Show 11 moreShow less1.9.4-2ubuntu1.21.9.4-2ubuntu1.31.9.4-2ubuntu1.41.9.4-2ubuntu1.51.9.4-2ubuntu1.61.9.4-2ubuntu1.81.9.4-2ubuntu1.91.9.4-2ubuntu1.111.9.4-2ubuntu1.11+esm11.9.4-2ubuntu1.11+esm21.9.4-2ubuntu1.11+esm3 | None known |
unboundUbuntu:22.04:LTS | before 1.13.1-1ubuntu5.15, plus listed versions 1.13.1-1ubuntu11.13.1-1ubuntu31.13.1-1ubuntu51.13.1-1ubuntu5.11.13.1-1ubuntu5.2 Show 10 moreShow less1.13.1-1ubuntu5.31.13.1-1ubuntu5.41.13.1-1ubuntu5.51.13.1-1ubuntu5.71.13.1-1ubuntu5.81.13.1-1ubuntu5.101.13.1-1ubuntu5.111.13.1-1ubuntu5.121.13.1-1ubuntu5.131.13.1-1ubuntu5.14 | 1.13.1-1ubuntu5.15 |
unboundUbuntu:24.04:LTS | before 1.19.2-1ubuntu3.8, plus listed versions 1.17.1-21.18.0-2ubuntu11.18.0-2ubuntu21.19.1-1ubuntu11.19.2-1ubuntu1 Show 8 moreShow less1.19.2-1ubuntu31.19.2-1ubuntu3.11.19.2-1ubuntu3.21.19.2-1ubuntu3.31.19.2-1ubuntu3.41.19.2-1ubuntu3.51.19.2-1ubuntu3.61.19.2-1ubuntu3.7 | 1.19.2-1ubuntu3.8 |
unboundUbuntu:25.10 | before 1.22.0-2ubuntu2.3, plus listed versions 1.22.0-1ubuntu11.22.0-2ubuntu11.22.0-2ubuntu21.22.0-2ubuntu2.11.22.0-2ubuntu2.2 | 1.22.0-2ubuntu2.3 |
unboundUbuntu:26.04:LTS | before 1.24.2-1ubuntu2.1, plus listed versions 1.22.0-2ubuntu21.22.0-2ubuntu41.24.2-1ubuntu11.24.2-1ubuntu2 | 1.24.2-1ubuntu2.1 |
unboundopenSUSE:Tumbleweed From an advisory covering 11 CVEs | before 1.25.1-1.1 | 1.25.1-1.1 |
unboundopenSUSE:Leap 16.0 From an advisory covering 11 CVEs | before 1.24.1-160000.2.1 | 1.24.1-160000.2.1 |
What each source reports
CVE List Score used 6.9
Degradation of service with unbounded NSEC3 hash calculations
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.
- Record
CVE-2026-42923- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/U:Amber - Weakness
- CWE-407
- Updated
- 2026-11-02
EUVDEUVD-2026-31081 6.9
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.
- Record
EUVD-2026-31081- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/U:Amber - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-8f6w-8h24-fw66 6.9
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator...
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.
- Record
GHSA-8f6w-8h24-fw66- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber - CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-407
- Updated
- 2026-11-02
NVD 6.9
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.
- Record
CVE-2026-42923- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber - CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-407
- Updated
- 2026-11-02
OSVALPINE-CVE-2026-42923 5.3
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.
- Record
ALPINE-CVE-2026-42923- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-02
OSV 5.3
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.
- Record
CVE-2026-42923- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-02
Show 23 moreShow less
OSVDEBIAN-CVE-2026-42923 5.3
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.
- Record
DEBIAN-CVE-2026-42923- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-02
OSVOESA-2026-2606 7.5
unbound security update
Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn't make custom builds or provide specific features to paying customers only.
Security Fix(es):
NLnet Labs Unbound 1.6.2 up to and including version 1.25.0 has a denial of service vulnerability when compiled with DNSCrypt support ('--enable-dnscrypt'). A bad DNSCrypt query could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow. A malicious actor can exploit the vulnerability with a single bad DNSCrypt query that its decrypted plaintext consists entirely of '0x00' bytes and does not contain the expected '0x80' marker. Unbound would then start reading more bytes than necessary until it finds a non-'0x00' byte. Based on the underlying memory allocator and the memory layout, it could lead to heap overflow while reading followed by a crash. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. If the heap overflow does not happen, Unbound's later packet checks will deny the packet. Unbound 1.25.1 contains a patch with a fix to bound reading in the given buffer space.(CVE-2026-32792)
NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.(CVE-2026-40622)
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.(CVE-2026-42534)
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code…
- Record
OESA-2026-2606- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-02
OSVOESA-2026-2607 7.5
unbound security update
Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn't make custom builds or provide specific features to paying customers only.
Security Fix(es):
NLnet Labs Unbound 1.6.2 up to and including version 1.25.0 has a denial of service vulnerability when compiled with DNSCrypt support ('--enable-dnscrypt'). A bad DNSCrypt query could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow. A malicious actor can exploit the vulnerability with a single bad DNSCrypt query that its decrypted plaintext consists entirely of '0x00' bytes and does not contain the expected '0x80' marker. Unbound would then start reading more bytes than necessary until it finds a non-'0x00' byte. Based on the underlying memory allocator and the memory layout, it could lead to heap overflow while reading followed by a crash. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. If the heap overflow does not happen, Unbound's later packet checks will deny the packet. Unbound 1.25.1 contains a patch with a fix to bound reading in the given buffer space.(CVE-2026-32792)
NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.(CVE-2026-40622)
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.(CVE-2026-42534)
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code…
- Record
OESA-2026-2607- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-02
OSVOESA-2026-2608 7.5
unbound security update
Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn't make custom builds or provide specific features to paying customers only.
Security Fix(es):
NLnet Labs Unbound 1.6.2 up to and including version 1.25.0 has a denial of service vulnerability when compiled with DNSCrypt support ('--enable-dnscrypt'). A bad DNSCrypt query could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow. A malicious actor can exploit the vulnerability with a single bad DNSCrypt query that its decrypted plaintext consists entirely of '0x00' bytes and does not contain the expected '0x80' marker. Unbound would then start reading more bytes than necessary until it finds a non-'0x00' byte. Based on the underlying memory allocator and the memory layout, it could lead to heap overflow while reading followed by a crash. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. If the heap overflow does not happen, Unbound's later packet checks will deny the packet. Unbound 1.25.1 contains a patch with a fix to bound reading in the given buffer space.(CVE-2026-32792)
NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.(CVE-2026-40622)
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.(CVE-2026-42534)
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code…
- Record
OESA-2026-2608- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-02
OSVOESA-2026-2609 7.5
unbound security update
Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn't make custom builds or provide specific features to paying customers only.
Security Fix(es):
NLnet Labs Unbound 1.6.2 up to and including version 1.25.0 has a denial of service vulnerability when compiled with DNSCrypt support ('--enable-dnscrypt'). A bad DNSCrypt query could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow. A malicious actor can exploit the vulnerability with a single bad DNSCrypt query that its decrypted plaintext consists entirely of '0x00' bytes and does not contain the expected '0x80' marker. Unbound would then start reading more bytes than necessary until it finds a non-'0x00' byte. Based on the underlying memory allocator and the memory layout, it could lead to heap overflow while reading followed by a crash. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. If the heap overflow does not happen, Unbound's later packet checks will deny the packet. Unbound 1.25.1 contains a patch with a fix to bound reading in the given buffer space.(CVE-2026-32792)
NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.(CVE-2026-40622)
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.(CVE-2026-42534)
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code…
- Record
OESA-2026-2609- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-02
OSVRHSA-2026:20357 7.5
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
- Record
RHSA-2026:20357- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-13
OSVRHSA-2026:97121 6.5
Red Hat Security Advisory: unbound security, bug fix, and enhancement update
- Record
RHSA-2026:97121- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L - Updated
- 2026-11-13
OSVRHSA-2026:97497 6.5
Red Hat Security Advisory: unbound security, bug fix, and enhancement update
- Record
RHSA-2026:97497- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L - Updated
- 2026-11-13
OSVRLSA-2026:97121 6.5
Moderate: unbound security, bug fix, and enhancement update
The unbound packages provide a validating, recursive, and caching DNS or DNSSEC resolver.
Security Fix(es):
unbound: Unbound DNS Cache Poisoning via Promiscuous Additional Section RRSet Acceptance (CVE-2026-42960)
unbound: Unbound DNSSEC Validator NSEC3 Hash Calculation Limit Bypass via Negative Cache Code Path Leading to DoS (CVE-2026-42923)
unbound: Unbound: Denial of Service due to locking inconsistency during RPZ XFR reload (CVE-2026-44608)
Bug Fix(es) and Enhancement(s):
Update to latest 1.26 (JIRA:Rocky Linux-246536)
[Rocky Linux-10][AppStream] Packages present in comps but missing from repo: unbound (JIRA:Rocky Linux-171309)
For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.
Additional Changes:
For detailed information on changes in this release, see the Rocky Linux 10 Release Notes linked from the References section.
- Record
RLSA-2026:97121- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L - Updated
- 2026-11-13
OSVRLSA-2026:97497 6.5
Moderate: unbound security, bug fix, and enhancement update
The unbound packages provide a validating, recursive, and caching DNS or DNSSEC resolver.
Security Fix(es):
unbound: Unbound DNS Cache Poisoning via Promiscuous Additional Section RRSet Acceptance (CVE-2026-42960)
unbound: Unbound DNSSEC Validator NSEC3 Hash Calculation Limit Bypass via Negative Cache Code Path Leading to DoS (CVE-2026-42923)
unbound: Unbound: Denial of Service due to locking inconsistency during RPZ XFR reload (CVE-2026-44608)
Bug Fix(es) and Enhancement(s):
- Update to latest 1.26 [rhel-9] (JIRA:Rocky Linux-246537)
For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.
Additional Changes:
For detailed information on changes in this release, see the Rocky Linux 9 Release Notes linked from the References section.
- Record
RLSA-2026:97497- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L - Updated
- 2026-11-13
OSVUBUNTU-CVE-2026-42923 6.9
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.
- Record
UBUNTU-CVE-2026-42923- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/U:Amber - CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-02
OSVAZL-87039No score
CVE-2026-42923 affecting package unbound for versions less than 1.25.1-1
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.
- Record
AZL-87039- Updated
- 2026-11-02
OSVCLSA-2026-1785318558No score
unbound: Fix of 2 CVEs
- CVE-2026-42923: cap NSEC3 hash calculations in the negative-cache DS proof and reject oversized NSEC3 salt
- CVE-2024-43168: reject negative port numbers in outgoing-port-permit/avoid to prevent an out-of-bounds write
- Record
CLSA-2026-1785318558- Updated
- 2026-11-02
OSVCLSA-2026-1785417704No score
unbound: Fix of 3 CVEs
- CVE-2026-50243: do not let response-ip/rpz rewrite a BOGUS answer; return SERVFAIL
- CVE-2026-42923: cap NSEC3 hash calculations in the negative-cache DS proof and reject oversized NSEC3 salt
- CVE-2024-43168: reject negative port numbers in outgoing-port-permit/avoid to prevent an out-of-bounds write
- Record
CLSA-2026-1785417704- Updated
- 2026-11-02
OSVCLSA-2026-1785489388No score
unbound: Fix of 3 CVEs
- CVE-2026-50243: do not let response-ip/rpz rewrite a BOGUS answer; return SERVFAIL
- CVE-2026-42923: cap NSEC3 hash calculations in the negative-cache DS proof and reject oversized NSEC3 salt
- CVE-2024-43168: reject negative port numbers in outgoing-port-permit/avoid to prevent an out-of-bounds write
- Record
CLSA-2026-1785489388- Updated
- 2026-11-02
OSVopenSUSE-SU-2026:10903-1No score
libunbound8-1.25.1-1.1 on GA media
These are all security issues fixed in the libunbound8-1.25.1-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2026:10903-1- Updated
- 2026-11-02
OSVopenSUSE-SU-2026:21083-1No score
Security update for unbound
This update for unbound fixes the following issues
- CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
- CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
- CVE-2026-40622: "Ghost domain name" variant (bsc#1265581).
- CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
- CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
- CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
- CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
- CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
- CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
- CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
- CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).
- Record
openSUSE-SU-2026:21083-1- Updated
- 2026-11-02
OSVSUSE-SU-2026:21874-1No score
Security update for unbound
This update for unbound fixes the following issues
- CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
- CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
- CVE-2026-40622: "Ghost domain name" variant (bsc#1265581).
- CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
- CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
- CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
- CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
- CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
- CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
- CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
- CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).
- Record
SUSE-SU-2026:21874-1- Updated
- 2026-11-02
OSVSUSE-SU-2026:21913-1No score
Security update for unbound
This update for unbound fixes the following issues
- CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
- CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
- CVE-2026-40622: "Ghost domain name" variant (bsc#1265581).
- CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
- CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
- CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
- CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
- CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
- CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
- CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
- CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).
- Record
SUSE-SU-2026:21913-1- Updated
- 2026-11-02
OSVSUSE-SU-2026:22160-1No score
Security update for unbound
This update for unbound fixes the following issues
- CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
- CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
- CVE-2026-40622: "Ghost domain name" variant (bsc#1265581).
- CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
- CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
- CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
- CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
- CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
- CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
- CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
- CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).
- Record
SUSE-SU-2026:22160-1- Updated
- 2026-11-02
OSVSUSE-SU-2026:22213-1No score
Security update for unbound
This update for unbound fixes the following issues
- CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
- CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
- CVE-2026-40622: "Ghost domain name" variant (bsc#1265581).
- CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
- CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
- CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
- CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
- CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
- CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
- CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
- CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).
- Record
SUSE-SU-2026:22213-1- Updated
- 2026-11-02
OSVSUSE-SU-2026:2281-1No score
Security update for unbound
This update for unbound fixes the following issues
- CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
- CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
- CVE-2026-40622: 'Ghost domain name' variant (bsc#1265581).
- CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
- CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
- CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
- CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
- CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
- CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
- CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
- CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).
- Record
SUSE-SU-2026:2281-1- Updated
- 2026-11-02
OSVSUSE-SU-2026:2369-1No score
Security update for unbound
This update for unbound fixes the following issues
- CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
- CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
- CVE-2026-40622: 'Ghost domain name' variant (bsc#1265581).
- CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
- CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
- CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
- CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
- CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
- CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
- CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
- CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).
- Record
SUSE-SU-2026:2369-1- Updated
- 2026-11-02
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, aliases, references | OSV | |
| affected, aliases, references | OSV | |
| affected, facts | ||
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
References
nlnetlabs.nl/downloads/unbound/CVE-2026-42923.txt
nvd.nist.gov/vuln/detail/CVE-2026-42923
github.com/advisories/GHSA-8f6w-8h24-fw66
security.alpinelinux.org/vuln/CVE-2026-42923
errata.tuxcare.com/els_os/almalinux9.2esu/CLSA-2026-1785318558.html
nvd.nist.gov/vuln/detail/CVE-2024-43168
Show 149 moreShow less
errata.tuxcare.com/els_os/tuxcare9.6esu/CLSA-2026-1785417704.html
nvd.nist.gov/vuln/detail/CVE-2026-50243
errata.tuxcare.com/els_os/centos-stream8els/CLSA-2026-1785489388.html
security-tracker.debian.org/tracker/CVE-2026-42923
openeuler.org/zh/security/security-bulletins/detail?id=openEuler-SA-2026-2606
nvd.nist.gov/vuln/detail/CVE-2026-32792
nvd.nist.gov/vuln/detail/CVE-2026-40622
nvd.nist.gov/vuln/detail/CVE-2026-42534
nvd.nist.gov/vuln/detail/CVE-2026-44390
openeuler.org/zh/security/security-bulletins/detail?id=openEuler-SA-2026-2607
nvd.nist.gov/vuln/detail/CVE-2026-44608
openeuler.org/zh/security/security-bulletins/detail?id=openEuler-SA-2026-2608
openeuler.org/zh/security/security-bulletins/detail?id=openEuler-SA-2026-2609
access.redhat.com/errata/RHSA-2026:20357
images.redhat.com
access.redhat.com/security/cve/CVE-2026-32792
access.redhat.com/security/updates/classification
access.redhat.com/security/cve/CVE-2026-42960
access.redhat.com/security/cve/CVE-2026-42923
access.redhat.com/security/cve/CVE-2026-40622
security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_20357.json
bugzilla.redhat.com/show_bug.cgi?id=2479779
cve.org/CVERecord?id=CVE-2026-32792
bugzilla.redhat.com/show_bug.cgi?id=2480127
cve.org/CVERecord?id=CVE-2026-40622
nlnetlabs.nl/downloads/unbound/CVE-2026-40622.txt
bugzilla.redhat.com/show_bug.cgi?id=2479825
cve.org/CVERecord?id=CVE-2026-42923
bugzilla.redhat.com/show_bug.cgi?id=2479821
cve.org/CVERecord?id=CVE-2026-42960
nvd.nist.gov/vuln/detail/CVE-2026-42960
access.redhat.com/errata/RHSA-2026:97121
docs.redhat.com/en/documentation/red_hat_enterprise_linux/10/html/10.3_release_notes/index
bugzilla.redhat.com/show_bug.cgi?id=2480126
issues.redhat.com/browse/RHEL-246536
security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_97121.json
access.redhat.com/security/cve/CVE-2026-42955
bugzilla.redhat.com/show_bug.cgi?id=2506144
cve.org/CVERecord?id=CVE-2026-42955
nvd.nist.gov/vuln/detail/CVE-2026-42955
nlnetlabs.nl/downloads/unbound/CVE-2026-42955.txt
access.redhat.com/security/cve/CVE-2026-44608
cve.org/CVERecord?id=CVE-2026-44608
nlnetlabs.nl/downloads/unbound/CVE-2026-44608.txt
access.redhat.com/security/cve/CVE-2026-44621
bugzilla.redhat.com/show_bug.cgi?id=2506149
cve.org/CVERecord?id=CVE-2026-44621
nvd.nist.gov/vuln/detail/CVE-2026-44621
nlnetlabs.nl/downloads/unbound/CVE-2026-44621.txt
access.redhat.com/security/cve/CVE-2026-44687
bugzilla.redhat.com/show_bug.cgi?id=2506130
cve.org/CVERecord?id=CVE-2026-44687
nvd.nist.gov/vuln/detail/CVE-2026-44687
nlnetlabs.nl/downloads/unbound/CVE-2026-44687.txt
access.redhat.com/security/cve/CVE-2026-46582
bugzilla.redhat.com/show_bug.cgi?id=2506139
cve.org/CVERecord?id=CVE-2026-46582
nvd.nist.gov/vuln/detail/CVE-2026-46582
nlnetlabs.nl/downloads/unbound/CVE-2026-46582.txt
access.redhat.com/security/cve/CVE-2026-50045
bugzilla.redhat.com/show_bug.cgi?id=2506136
cve.org/CVERecord?id=CVE-2026-50045
nvd.nist.gov/vuln/detail/CVE-2026-50045
nlnetlabs.nl/downloads/unbound/CVE-2026-50045.txt
access.redhat.com/security/cve/CVE-2026-50046
bugzilla.redhat.com/show_bug.cgi?id=2506138
cve.org/CVERecord?id=CVE-2026-50046
nvd.nist.gov/vuln/detail/CVE-2026-50046
nlnetlabs.nl/downloads/unbound/CVE-2026-50046.txt
access.redhat.com/security/cve/CVE-2026-50243
bugzilla.redhat.com/show_bug.cgi?id=2506132
cve.org/CVERecord?id=CVE-2026-50243
nlnetlabs.nl/downloads/unbound/CVE-2026-50243.txt
access.redhat.com/security/cve/CVE-2026-50248
bugzilla.redhat.com/show_bug.cgi?id=2506129
cve.org/CVERecord?id=CVE-2026-50248
nvd.nist.gov/vuln/detail/CVE-2026-50248
nlnetlabs.nl/downloads/unbound/CVE-2026-50248.txt
access.redhat.com/security/cve/CVE-2026-50251
bugzilla.redhat.com/show_bug.cgi?id=2506150
cve.org/CVERecord?id=CVE-2026-50251
nvd.nist.gov/vuln/detail/CVE-2026-50251
nlnetlabs.nl/downloads/unbound/CVE-2026-50251.txt
access.redhat.com/security/cve/CVE-2026-52863
bugzilla.redhat.com/show_bug.cgi?id=2506141
cve.org/CVERecord?id=CVE-2026-52863
nvd.nist.gov/vuln/detail/CVE-2026-52863
nlnetlabs.nl/downloads/unbound/CVE-2026-52863.txt
access.redhat.com/security/cve/CVE-2026-54478
bugzilla.redhat.com/show_bug.cgi?id=2506146
cve.org/CVERecord?id=CVE-2026-54478
nvd.nist.gov/vuln/detail/CVE-2026-54478
nlnetlabs.nl/downloads/unbound/CVE-2026-54478.txt
access.redhat.com/security/cve/CVE-2026-55708
bugzilla.redhat.com/show_bug.cgi?id=2506131
cve.org/CVERecord?id=CVE-2026-55708
nvd.nist.gov/vuln/detail/CVE-2026-55708
nlnetlabs.nl/downloads/unbound/CVE-2026-55708.txt
access.redhat.com/security/cve/CVE-2026-55717
bugzilla.redhat.com/show_bug.cgi?id=2506135
cve.org/CVERecord?id=CVE-2026-55717
nvd.nist.gov/vuln/detail/CVE-2026-55717
nlnetlabs.nl/downloads/unbound/CVE-2026-55717.txt
access.redhat.com/security/cve/CVE-2026-56416
bugzilla.redhat.com/show_bug.cgi?id=2506137
cve.org/CVERecord?id=CVE-2026-56416
nvd.nist.gov/vuln/detail/CVE-2026-56416
nlnetlabs.nl/downloads/unbound/CVE-2026-56416.txt
access.redhat.com/security/cve/CVE-2026-56444
bugzilla.redhat.com/show_bug.cgi?id=2506142
cve.org/CVERecord?id=CVE-2026-56444
nvd.nist.gov/vuln/detail/CVE-2026-56444
nlnetlabs.nl/downloads/unbound/CVE-2026-56444.txt
access.redhat.com/errata/RHSA-2026:97497
docs.redhat.com/en/documentation/red_hat_enterprise_linux/9/html/9.9_release_notes/index
security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_97497.json
errata.rockylinux.org/RLSA-2026:97121
errata.rockylinux.org/RLSA-2026:97497
suse.com/support/update/announcement/2026/suse-su-202621874-1
bugzilla.suse.com/1265578
bugzilla.suse.com/1265580
bugzilla.suse.com/1265581
bugzilla.suse.com/1265582
bugzilla.suse.com/1265583
bugzilla.suse.com/1265584
bugzilla.suse.com/1265585
bugzilla.suse.com/1265586
bugzilla.suse.com/1265587
bugzilla.suse.com/1265588
bugzilla.suse.com/1265589
suse.com/security/cve/CVE-2026-32792
suse.com/security/cve/CVE-2026-33278
suse.com/security/cve/CVE-2026-40622
suse.com/security/cve/CVE-2026-41292
suse.com/security/cve/CVE-2026-42534
suse.com/security/cve/CVE-2026-42923
suse.com/security/cve/CVE-2026-42944
suse.com/security/cve/CVE-2026-42959
suse.com/security/cve/CVE-2026-42960
suse.com/security/cve/CVE-2026-44390
suse.com/security/cve/CVE-2026-44608
suse.com/support/update/announcement/2026/suse-su-202621913-1
suse.com/support/update/announcement/2026/suse-su-202622160-1
suse.com/support/update/announcement/2026/suse-su-202622213-1
suse.com/support/update/announcement/2026/suse-su-20262281-1
suse.com/support/update/announcement/2026/suse-su-20262369-1
ubuntu.com/security/CVE-2026-42923
nlnetlabs.nl/news/2026/May/20/unbound-1.25.1-released
ubuntu.com/security/notices/USN-8282-1
Left out here: the rest of 4 source descriptions. The JSON record has them.