Heap-based buffer overflow in Unbound - CVE-2026-81634
Published: September 16, 2026 / Updated: September 19, 2026
Vulnerability identifier: #VU150192
CSH Severity: Low
CVSS v4: 0 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-81634
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause memory corruption.
The vulnerability exists due to improper buffer length validation in the RRSet canonicalisation routine when processing a 255-length query name with a large TCP response. A remote attacker can provide a crafted DNS response to cause memory corruption.
Canonicalisation occurs before DNSSEC validation.
Affected software
Unbound
Fedora
unbound
Fedora
unbound
How to mitigate CVE-2026-81634
Install security update from vendor's website.
Unbound - update to 1.26.1
unbound - addressed in versions 1.26.1-1.fc43, 1.26.1-1.fc44, 1.26.1-1.fc45
unbound - addressed in versions 1.26.1-1.fc43, 1.26.1-1.fc44, 1.26.1-1.fc45