Vulnerability in NLnet Labs NSD

[ Description ]Official description

Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• BSI CERT-Bund29 Sep 2026WID-SEC-2026-3663

  OpenBSD: Multiple vulnerabilities Translated from German

  CVE-2026-12245CVE-2026-19401CVE-2026-18664+5 more CVEs

[ References ]References

• www.nlnetlabs.nl/downloads/nsd/CVE-2026-19401.txtvendor-advisory