CVE-2026-101341: Stack overwrite from specially formatted TXT-DATA RDATA field
Tokens of text in RDATA (of for example TXT records) under 32 bytes are not checked to stay within the space reserved for the RDATA allowing for arbitrary sized out of bound stack writes, including an overwrite of a callback function pointer which is called directly after parse. Zone files which are written out by NSD itself, such 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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
NSDto a version that resolves this vulnerability.Fixed in 4.15.3
Event History
Frequently Asked Questions
Which NSD deployments are exposed to this issue?
Deployments that directly feed NSD zone files containing specially formatted TXT RDATA are exposed. Zones written out by NSD itself, including zones for which the instance acts as a secondary, are not formatted in the affected way.
What must an attacker control to exploit the vulnerability?
An attacker needs a way to cause a crafted zone file to be fed directly to NSD. This could include control of an operator-managed provisioning system that supplies zone files to NSD.
What is the practical impact of a successful exploit?
The malformed TXT RDATA can produce arbitrarily sized out-of-bounds stack writes. The overwrite can reach a callback function pointer that NSD calls immediately after parsing.