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VULNERABILITIES

CVE-2026-81634 Details

Description

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.

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:7.5 HIGHVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References to Advisories, Solutions, and Tools

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URLSource(s)Tag(s)
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81634.txt [email protected]PatchVendor Advisory

Weakness Enumeration

CWE-IDCWE NameSource
CWE-122Heap-based Buffer Overflow[email protected]

Affected Products

ProductVersions
nlnetlabs unbound
< 1.26.1

CPE

  • cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*

Remediation

  • No remediation found in references.

Change History

3 change records found show changes

QUICK INFO

CVE Dictionary Entry:
CVE-2026-81634
NVD Published Date:
Sep 16, 2026
NVD Last Modified:
Sep 23, 2026
Source:
[email protected]
CVE-2026-81634 Details - Not Deferred