CVE-2026-81634
Possible heap buffer overflow during DNSSEC canonicalization
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-122 |
| Vendor | nlnet labs |
| Product | unbound |
| Published | Sep 16, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality
Integrity
Availability
Affected Versions
NLnet Labs / Unbound
0 < 1.26.1
References
Credits
Vlatko Kosturjak (Marlink Cyber)