CVE-2026-19401
Remote UDP DoS by sending multiple DNS Cookie options
Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.
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
- High
Exploit likelihood
What each source reports
CVE List Score used
Remote UDP DoS by sending multiple DNS Cookie options
Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.
- Record
CVE-2026-19401- CVSS 4.0
- 8.2 High
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Weakness
- CWE-617, CWE-400
- Updated
- 2026-11-02
EUVDEUVD-2026-66349
Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.
- Record
EUVD-2026-66349- CVSS 4.0
- 8.2 High
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-v29p-5fvf-m7p8
Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a...
Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.
- Record
GHSA-v29p-5fvf-m7p8- CVSS 4.0
- 8.2 High
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/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:X - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-400
- Updated
- 2026-11-02
NVD
Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.
- Record
CVE-2026-19401- CVSS 4.0
- 8.2 High
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/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:X - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-400, CWE-617
- Updated
- 2026-11-02
OSV
Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.
- Record
CVE-2026-19401- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-19401
Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.
- Record
DEBIAN-CVE-2026-19401- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-19401
Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.
- Record
UBUNTU-CVE-2026-19401- CVSS 4.0
- 8.2 High
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
nsdDebian:12 |
All versions, plus listed versions 4.10.1-14.10.1~rc2-14.10.1~rc2-24.11.0-14.11.1-1 Show 20 moreShow less4.12.0-14.12.0-24.13.0-14.13.0-24.13.0-34.13.0-44.13.0-54.13.0-64.14.0-14.14.1-14.14.2-14.14.3-14.15.0-14.15.0~rc1-14.15.1-14.15.2-14.6.1-14.7.0-14.8.0-14.9.1-1 |
None known |
nsdDebian:13 |
All versions, plus listed versions 4.12.0-14.12.0-24.13.0-14.13.0-24.13.0-3 Show 11 moreShow less4.13.0-44.13.0-54.13.0-64.14.0-14.14.1-14.14.2-14.14.3-14.15.0-14.15.0~rc1-14.15.1-14.15.2-1 |
None known |
nsdDebian:14 |
before 4.15.1-1, plus listed versions 4.12.0-14.12.0-24.13.0-14.13.0-24.13.0-3 Show 9 moreShow less4.13.0-44.13.0-54.13.0-64.14.0-14.14.1-14.14.2-14.14.3-14.15.0-14.15.0~rc1-1 |
4.15.1-1 |
nsdUbuntu:Pro:16.04:LTS |
All versions, plus listed versions 4.1.2-14.1.6-14.1.7-14.1.7-1ubuntu0.1~esm1 |
None known |
nsdUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 4.1.16-1build14.1.17-14.1.17-1build14.1.17-1ubuntu0.1~esm1 |
None known |
nsdUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 4.1.26-14.1.26-1build14.1.26-1ubuntu0.1~esm1 |
None known |
nsdUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 4.3.5-14.3.7-14.3.8-14.3.8-1build14.3.9-14.3.9-1ubuntu0.1~esm1 |
None known |
nsdUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 4.7.0-14.8.0-14.8.0-1build14.8.0-1build34.8.0-1ubuntu0.1~esm1 |
None known |
nsdUbuntu:26.10 |
All versions, plus listed versions 4.14.0-14.14.2-14.14.3-14.15.0-14.15.0-1build1 |
None known |
nsdUbuntu:Pro:26.04:LTS |
All versions, plus listed versions 4.12.0-14.13.0-64.14.0-14.14.0-1ubuntu0.1~esm1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-19401 is a high vulnerability (CVSS 8.2) in Nlnet Labs Nsd, published August 26, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.46%, the 40th percentile. Fixed in nsd 4.15.1-1.