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Vulnerability · Published Oct 14, 2026 · Assigned by NLnet Labs

CVE-2026-101338Stack overwrite from a specially crafted and formatted SVCB or HTTPS RR

High 8.7

In plain English

A high-severity stack buffer overflow in NSD from NLnet Labs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.7High
Exploit odds (30 days)0.3%top 72.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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).

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.21nsd4.11.1-r1ALPINE-CVE-2026-101338
Alpine:v3.22nsd4.12.0-r1ALPINE-CVE-2026-101338
Alpine:v3.23nsd4.13.0-r1ALPINE-CVE-2026-101338
Alpine:v3.24nsd4.14.3-r1ALPINE-CVE-2026-101338
Debian:12nsdno fix listedDEBIAN-CVE-2026-101338
Debian:13nsdno fix listedDEBIAN-CVE-2026-101338
Debian:14nsd4.15.3-1DEBIAN-CVE-2026-101338
Ubuntu:26.10nsdno fix listedUBUNTU-CVE-2026-101338

Affected products (as reported)

VendorProductVersions
NLnet Labs NSD 4.10.0 – before 4.15.3

Weakness: CWE-121 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References