Vulnerability Details CVE-2026-91768
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.004
EPSS Ranking 31.4%
CVSS Severity
CVSS v3 Score 6.5