CVE-2026-81634 — Possible heap buffer overflow during DNSSEC canonicalization
In NLnet Labs Unbound up to and including 1.26.0, a 255 length query name with a large TCP response can lead to a heap buffer overflow during the RRSet canonicalisation routine.…
Published: 2026-09-16 · CVSS: 7.5 · CVSS 3.1
In NLnet Labs Unbound up to and including 1.26.0, a 255 length query name with a large TCP response can lead to a heap buffer overflow during the RRSet canonicalisation routine. This is caused by missing to add the first owner name into the buffer length check. A malicious actor operating a malicious name server or tampering with an incoming response to Unbound (canonicalisation happens before DNSSEC validation), can trigger the vulnerability.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7