Inefficient Algorithmic Complexity in Unbound - CVE-2026-85501
Published: September 16, 2026 / Updated: September 19, 2026
Vulnerability identifier: #VU150196
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-85501
CWE-ID: CWE-407
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to inefficient algorithmic complexity in the DNSSEC validator's Zone, Algo, KeyTag matching mechanism when processing DNS responses containing numerous mismatched DNSKEY, RRSIG, and DS records. A remote attacker can provide a crafted DNS response to cause a denial of service.
Affected software
Unbound
Fedora
unbound
Fedora
unbound
How to mitigate CVE-2026-85501
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