Input validation error in PowerDNS Recursor - CVE-2026-85556
Published: October 21, 2026
Vulnerability identifier: #VU156687
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-85556
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass EDNS Client Subnet hardening in PowerDNS Recursor and cause acceptance of an EDNS option that should be rejected.
The vulnerability exists due to missing owner-name validation in OPT resource record handling when processing EDNS records whose owner is not the DNS root. A remote attacker can supply a specially crafted record with a non-root owner name to bypass the validation checks and have an EDNS option accepted incorrectly.
Affected software
PowerDNS Recursor
How to mitigate CVE-2026-85556
Install security update from vendor's website.
PowerDNS Recursor - addressed in versions 5.3.12, 5.4.8