CVE-2026-91769 — TLS Hostname Verification Falls Back to CN After SAN Mismatch

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
PHP Group / PHP	affected 8.2.* before 8.2.34; affected 8.3.* before 8.3.35; affected 8.4.* before 8.4.26; affected 8.5.* before 8.5.11

CWE

CWE-297

References

https://github.com/php/php-src/security/advisories/GHSA-vvx9-73fr-5jjx

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.