This page tracks the Ubuntu fix status. The vulnerability itself is described on the main CVE page. View CVE-2026-81634 →

UBUNTU-CVE-2026-81634

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 RRSe...

Original description

The description as published by the source.

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: OSV.dev (Open Source Vulnerabilities) OSV