CVE-2026-91768: PHP Group PHP

Medium severity, CVSS 6.5. EPSS: 0.6% chance of exploitation in the next 30 days.

The IPv6 branch of the FastCGI client access check compares only the first 12 bytes of a 16-byte IPv6 address, so listen.allowed_clients matches on a /96 prefix instead of the exact address. An attacker who can source an address sharing the first 96 bits with an allowed one passes the check and reaches the FastCGI endpoint.

Affected products

• PHP Group PHP: from 8.2, before 8.2.34 (fixed in 8.2.34); from 8.3, before 8.3.35 (fixed in 8.3.35); from 8.4, before 8.4.26 (fixed in 8.4.26); from 8.5, before 8.5.11 (fixed in 8.5.11)

Published 2026-09-25. Last modified 2026-09-29.