CVE-2026-81634 (GCVE-0-2026-81634)

Vulnerability from cvelistv5 – Published: 2026-09-16 08:30 – Updated: 2026-09-16 14:32
VLAI
Title
Possible heap buffer overflow during DNSSEC canonicalization
Summary
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.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-16 14:32 UTC
CWE
  • CWE-122 - Heap-based Buffer Overflow
Assigner
NLnet Labs CNA
CNA scorecard B 82/100 over 76 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
NLnet Labs Unbound Affected: 0 , < 1.26.1 (semver)
guessed Create a notification for this product.
Date Public
2026-09-16 00:00
Credits
Vlatko Kosturjak (Marlink Cyber)
Show details on NVD website
To clipboard 

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