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.
Advisories
Source ID Title
Debian DSA Debian DSA DSA-6514-1 php8.4 security update
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Sat, 26 Sep 2026 08:15:00 +0000

Type Values Removed Values Added
First Time appeared Php Group
Php Group php
Vendors & Products Php Group
Php Group php

Sat, 26 Sep 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-940
References
Metrics threat_severity

None

threat_severity

Moderate


Fri, 25 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
Description 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.
Title IPv6 ACL bypass in FastCGI listen.allowed_clients due to partial address comparison (memcmp 12 bytes)
Weaknesses CWE-1023
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'}


Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: php

Published:

Updated: 2026-09-25T21:07:30.950Z

Reserved: 2026-09-15T00:42:30.045Z

Link: CVE-2026-91768

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-25T22:18:49.807

Modified: 2026-09-25T22:18:49.807

Link: CVE-2026-91768

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-09-25T21:07:30Z

Links: CVE-2026-91768 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-26T08:00:10Z

Weaknesses