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CVE-2026-101338

Stack overwrite from a specially crafted and formatted SVCB or HTTPS RR

8.7 HighFix available

When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter may overwrite the stack, and once beyond the limit, the base64 decoder can write attacker controlled data of unlimited size. Zone files which are written out by NSD itself, such as for zones for which the NSD instance is secondary, will not be formatted like this. The zone file must be fed to NSD directly, (but it could come, for example, from an operator controlled provisioning system).

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.34%Unchanged since Oct 15, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.7

Stack overwrite from a specially crafted and formatted SVCB or HTTPS RR

When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter may overwrite the stack, and once beyond the limit, the base64 decoder can write attacker controlled data of unlimited size. Zone files which are written out by NSD itself, such as for zones for which the NSD instance is secondary, will not be formatted like this. The zone file must be fed to NSD directly, (but it could come, for example, from an operator controlled provisioning system).

Record
CVE-2026-101338
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-121
Updated
2026-11-02
EUVDEUVD-2026-100983 8.7

When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter may overwrite the stack, and once beyond the limit, the base64 decoder can write attacker controlled data of unlimited size. Zone files which are written out by NSD itself, such as for zones for which the NSD instance is secondary, will not be formatted like this. The zone file must be fed to NSD directly, (but it could come, for example, from an operator controlled provisioning system).

Record
EUVD-2026-100983
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-r5wh-92fx-cv6j 8.7

When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter...

When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter may overwrite the stack, and once beyond the limit, the base64 decoder can write attacker controlled data of unlimited size. Zone files which are written out by NSD itself, such as for zones for which the NSD instance is secondary, will not be formatted like this. The zone file must be fed to NSD directly, (but it could come, for example, from an operator controlled provisioning system).

Record
GHSA-r5wh-92fx-cv6j
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/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
Weakness
CWE-121
Updated
2026-11-02
NVD 8.7

When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter may overwrite the stack, and once beyond the limit, the base64 decoder can write attacker controlled data of unlimited size. Zone files which are written out by NSD itself, such as for zones for which the NSD instance is secondary, will not be formatted like this. The zone file must be fed to NSD directly, (but it could come, for example, from an operator controlled provisioning system).

Record
CVE-2026-101338
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/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
Weakness
CWE-121
Updated
2026-11-02
OSVALPINE-CVE-2026-101338 8.7

When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter may overwrite the stack, and once beyond the limit, the base64 decoder can write attacker controlled data of unlimited size. Zone files which are written out by NSD itself, such as for zones for which the NSD instance is secondary, will not be formatted like this. The zone file must be fed to NSD directly, (but it could come, for example, from an operator controlled provisioning system).

Record
ALPINE-CVE-2026-101338
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/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
Updated
2026-11-03
OSVDEBIAN-CVE-2026-101338 8.7

When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter may overwrite the stack, and once beyond the limit, the base64 decoder can write attacker controlled data of unlimited size. Zone files which are written out by NSD itself, such as for zones for which the NSD instance is secondary, will not be formatted like this. The zone file must be fed to NSD directly, (but it could come, for example, from an operator controlled provisioning system).

Record
DEBIAN-CVE-2026-101338
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/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
Updated
2026-11-02
OSVUBUNTU-CVE-2026-101338 8.7

When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter may overwrite the stack, and once beyond the limit, the base64 decoder can write attacker controlled data of unlimited size. Zone files which are written out by NSD itself, such as for zones for which the NSD instance is secondary, will not be formatted like this. The zone file must be fed to NSD directly, (but it could come, for example, from an operator controlled provisioning system).

Record
UBUNTU-CVE-2026-101338
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
nsd
Alpine:v3.21
before 4.11.1-r1
4.11.1-r1
nsd
Alpine:v3.22
before 4.12.0-r1
4.12.0-r1
nsd
Alpine:v3.23
before 4.13.0-r1
4.13.0-r1
nsd
Alpine:v3.24
before 4.14.3-r1
4.14.3-r1
nsd
Debian: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 22 moreShow less
4.12.0-14.12.0-24.13.0-14.13.0-24.13.0-34.13.0-44.13.0-54.13.0-64.14.0-14.14.1-14.14.2-14.14.3-14.15.0-14.15.0~rc1-14.15.1-14.15.2-14.15.3-14.15.4-14.6.1-14.7.0-14.8.0-14.9.1-1
None known
nsd
Debian:13
All versions, plus listed versions
4.12.0-14.12.0-24.13.0-14.13.0-24.13.0-3
Show 13 moreShow less
4.13.0-44.13.0-54.13.0-64.14.0-14.14.1-14.14.2-14.14.3-14.15.0-14.15.0~rc1-14.15.1-14.15.2-14.15.3-14.15.4-1
None known
nsd
Debian:14
before 4.15.3-1, plus listed versions
4.12.0-14.12.0-24.13.0-14.13.0-24.13.0-3
Show 11 moreShow less
4.13.0-44.13.0-54.13.0-64.14.0-14.14.1-14.14.2-14.14.3-14.15.0-14.15.0~rc1-14.15.1-14.15.2-1
4.15.3-1
nsd
Ubuntu: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
nsd
Ubuntu: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
nsd
Ubuntu:Pro:20.04:LTS
All versions, plus listed versions
4.1.26-14.1.26-1build14.1.26-1ubuntu0.1~esm1
None known
Show 4 moreShow less
Affected packages
PackageAffectedFixed
nsd
Ubuntu: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
nsd
Ubuntu: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
nsd
Ubuntu: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
nsd
Ubuntu: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

History
RecordedChangedSources
affectedOSV
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-101338 is a high vulnerability (CVSS 8.7) in Nlnet Labs Nsd, published October 14, 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 nsd 4.11.1-r1.

References

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