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 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.
- Published Sep 16, 2026
- CVSS 7.5 high
- 0.5% chance of exploitation in the next 30 days (EPSS)
- A fix is available