CVE-2026-81634
highIn 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 canonic…
Vendor / product: Nlnetlabs — unbound
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.
CVSS
7.5
7.5 (CVSS v3.1)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Severity source: NVD CVSS v3.1 (sep@nlnetlabs.nl)
Timeline (UTC)
Published: 2026-09-16 09:17
Modified: 2026-09-23 19:51
NVD status: Analyzed
Last synced 1 day ago
Verified against the source API 2026-10-27 06:54 UTC
Exploitation
Not listed in CISA KEV (as of last catalog sync)
Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).
Affected products
nlnetlabs / unbound <1.26.1
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
Vendor advisory: https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81634.txt
Patch / mitigation: https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81634.txt
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81634.txt sep@nlnetlabs.nl
Data sources
NVD CVE API 2.0 — fetched 2026-10-27 06:54 UTC · record ↗