CVE-2026-91768 — MEDIUM (6.5)

Vulnerability 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.

CVSS Score

6.5

MEDIUM

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector

ADJACENT_NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

HIGH

Integrity

NONE

Availability

NONE

Related Weaknesses (CWE)

CWE-1023

References

https://github.com/php/php-src/security/advisories/GHSA-62xp-839h-2637

FAQ

What is CVE-2026-91768?

CVE-2026-91768 is a vulnerability with a CVSS score of 6.5 (MEDIUM). 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 attack...

How severe is CVE-2026-91768?

CVE-2026-91768 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-91768?

Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.