CVE-2026-91768CWE-1023

CVE-2026-91768

Medium · published September 26, 2026

CVSS v3.1
6.5
EPSS
1%
Percentile
45.8
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.5 · MEDIUM
Vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00561 · 45.8th percentile
Weakness
CWE-1023 · Incomplete Comparison with Missing Factors
Published
2026-09-26T02:18Z
References (1)
https://github.com/php/php-src/security/advisories/GHSA-62xp-839h-2637 · [email protected]
EPSS history
Timeline
  • 27 SEP 03:28Z
    EPSS moved — → 1%
    epss
  • 25 SEP 21:07Z
    IPv6 ACL bypass in FastCGI listen.allowed_clients due to partial address comparison (memcmp 12 bytes)
    cvelistv5