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CVE-2026-101337

Stack overwrite from specially formatted base64 RDATA field

8.7 HighFix available

CVE-2026-101337 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.

When base64 data is split up in pieces, of 3 character or less, tokens were incorrectly calculated to produce 0 bytes. This enables attackers to overwrite the stack with up to 64K of attacker controlled data. 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 specially formatted base64 RDATA field

When base64 data is split up in pieces, of 3 character or less, tokens were incorrectly calculated to produce 0 bytes. This enables attackers to overwrite the stack with up to 64K of attacker controlled data. 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-2026-101337
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-2026-100982 8.7

When base64 data is split up in pieces, of 3 character or less, tokens were incorrectly calculated to produce 0 bytes. This enables attackers to overwrite the stack with up to 64K of attacker controlled data. 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-2026-100982
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-w2rq-89vw-p64m 8.7

When base64 data is split up in pieces, of 3 character or less, tokens were incorrectly...

When base64 data is split up in pieces, of 3 character or less, tokens were incorrectly calculated to produce 0 bytes. This enables attackers to overwrite the stack with up to 64K of attacker controlled data. 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-w2rq-89vw-p64m
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 base64 data is split up in pieces, of 3 character or less, tokens were incorrectly calculated to produce 0 bytes. This enables attackers to overwrite the stack with up to 64K of attacker controlled data. 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-2026-101337
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-2026-101337 8.7

When base64 data is split up in pieces, of 3 character or less, tokens were incorrectly calculated to produce 0 bytes. This enables attackers to overwrite the stack with up to 64K of attacker controlled data. 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-2026-101337
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-2026-101337 8.7

When base64 data is split up in pieces, of 3 character or less, tokens were incorrectly calculated to produce 0 bytes. This enables attackers to overwrite the stack with up to 64K of attacker controlled data. 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-2026-101337
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-2026-101337 8.7

When base64 data is split up in pieces, of 3 character or less, tokens were incorrectly calculated to produce 0 bytes. This enables attackers to overwrite the stack with up to 64K of attacker controlled data. 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-2026-101337
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
WhenChangedSources
2026-11-03affectedOSV
2026-11-02createdCVE List, EUVD, GitHub Advisories, NVD, OSV

References

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