CVE-2026-101337 Stack overwrite from specially formatted base64 RDATA field
Attackers can overwrite the stack via specially formatted base64 RDATA fields in zone files, potentially leading to code execution.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-101337?
CVE-2026-101337 is a high-severity memory corruption vulnerability in NLnet Labs NSD, published on 14 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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).
Weakness: CWE-121
Which versions are affected by CVE-2026-101337?
How do I fix CVE-2026-101337?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-101337 being exploited?
There is no known exploitation of CVE-2026-101337 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-101337, DEBIAN-CVE-2026-101337, GHSA-w2rq-89vw-p64m, UBUNTU-CVE-2026-101337.