Buffer overflow in PHP
CVE-2026-91767
php_openssl_matches_wildcard_name() in ext/openssl/xp_ssl.c underflows the length argument passed to memchr() when a TLS server certificate presents a wildcard name whose literal characters are together longer than the hostname being verified. A malicious server presenting such a certificate makes the PHP client read up to SIZE_MAX bytes past the end of a heap allocation. The path is reachable from any default client stream, because verify_peer_name is enabled by default.
Vulnerability class: Buffer Overflow
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: 0.001 (1.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 1st percentile — 1.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.001 · change: -0.000
Affected products
Weakness classification (CWE)
References
- github.com/php/php-src/security/advisories/GHSA-xr7j-rvgx-xq5p (vendor-advisory, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-91767?
- CVE-2026-91767 is a medium-severity vulnerability in PHP, classified under Heap-based Buffer Overflow. CVSS score: 6.5/10. Published 2026-09-25.
- How severe is CVE-2026-91767?
- Medium severity. CVSS v3 base score is 6.5 out of 10.