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CVE-2026-91769GHSA-vvx9-73fr-5jjx

PHP: TLS Hostname Verification Falls Back to CN After SAN Mismatch

PHP Group PHPRuntimes & languages
Open in ThreatlineRecord JSON
CVSS
4.3Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.14%Chance of exploitation activity in the next 30 days, higher than 2% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in8.2.34Also 8.3.35, 8.4.26 and 1 moreCVE List
Published25 Sep 2026Updated 4 Oct 2026CVE List

What fixes it

Show all 8 fixed versions

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

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.

Text from CVE List

Affected versions 8

  • PHPaffected: 8.2.* before 8.2.34CVE List
  • PHPaffected: 8.3.* before 8.3.35CVE List
  • PHPaffected: 8.4.* before 8.4.26CVE List
  • PHPaffected: 8.5.* before 8.5.11CVE List
  • ext-openssl, php<8.2.34GitHub
  • ext-openssl, php<8.3.35GitHub
  • ext-openssl, php<8.4.26GitHub
  • ext-openssl, php<8.5.11GitHub

References 1