CVE-2026-81634
highpriority · track · 0EPSS 0.005 · 40 %ileDEUSEPSS · scored 2026-10-21
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
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.9–7.5
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (13)
Products and version ranges known to be affected.
advisories (1)
Vendor and ecosystem advisories describing this.
- WID-SEC-W-2026-3392Unbound: Mehrere SchwachstellenDeutsch2026-09-15csaf · cert_bundDE
Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Unbound ausnutzen, um Sicherheitsmaßnahmen zu umgehen, Speicher zu korrumpieren, einen Denial of Service zu verursachen oder Code auszuführen.
sources
Which sources assert this record, and when.
references (1) nvd
External citations — patches, advisories, analysis.
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81634.txtPatchVendor Advisory
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