CVE-2026-91769
TLS Hostname Verification Falls Back to CN After SAN Mismatch
Description
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.
No summary for this CVE yet.
CVSS Vector Breakdown
Exploitability
AV:AAttack VectorAdjacent
AC:LAttack ComplexityLow
PR:NPrivileges RequiredNone
UI:NUser InteractionNone
Scope
S:UScopeUnchanged
Impact
C:LConfidentialityLow
I:NIntegrityNone
A:NAvailabilityNone
Weaknesses
Affected Products
PHP Group
oss-projectaka php, pear
Exploitability
No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
References
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