Out-of-bounds read in PowerDNS Recursor - CVE-2026-85559
Published: October 21, 2026
Vulnerability identifier: #VU156690
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-2026-85559
CWE-ID: CWE-125
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service through a potential crash of PowerDNS Recursor.
The vulnerability exists due to an out-of-bounds read in findScopeZero when checking incoming EDNS Client Subnet data using an incorrect length bound. A remote attacker can supply specially crafted input to trigger a read beyond the valid bounds and potentially crash the Recursor.
The issue only applies when incoming.use_incoming_edns_subnet is enabled.
Affected software
PowerDNS Recursor
How to mitigate CVE-2026-85559
Install security update from vendor's website.
PowerDNS Recursor - addressed in versions 5.3.12, 5.4.8