Vulnerability in PHP
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.004 (31.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 32nd percentile — 31.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.004 · change: -0.002
Affected products
Weakness classification (CWE)
References
- github.com/php/php-src/security/advisories/GHSA-62xp-839h-2637 (vendor-advisory, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-91768?
- CVE-2026-91768 is a medium-severity vulnerability in PHP, classified under CWE-1023. CVSS score: 6.5/10. Published 2026-09-25.
- How severe is CVE-2026-91768?
- Medium severity. CVSS v3 base score is 6.5 out of 10.