CVE-2026-91769

MediumCVSS 4.3

Published: 25/09/2026(UTC)Updated: 23/10/2026(UTC)Translated: 26/09/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.14%

3th percentile - higher than 3% of all known CVEs

Summary

PHP's OpenSSL stream peer verification checks subjectAltName entries first and falls back to Common Name when no entry matches. RFC 6125 requires CN to be ignored once the certificate presents any service identity, so a certificate with a non-matching DNS SAN was still accepted when its CN matched the requested peer_name.

Risk Assessment

A certificate trusted by the client for one name can be used to impersonate another, enabling man-in-the-middle attacks and data interception.

Recommendation

Update PHP to a version containing the fix or disable CN fallback in certificate verification if possible.

Other vulnerabilities in PHP OpenSSL

CVE-2026-91767Medium
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.

Original NVD description (English source)

PHP's OpenSSL stream peer verification checks the certificate's subjectAltName entries first and, whenever no entry matches, falls back to the Common Name. RFC 6125 requires the CN to be ignored once the certificate presents any service identity, so a certificate carrying a non-matching DNS SAN was still accepted when its CN matched the requested peer_name. A certificate trusted by the client for one name can therefore be used to impersonate another.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS