CVE-2026-91769: CWE-297 Improper validation of certificate with host mismatch in PHP Group PHP
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.
AI Analysis
Technical Summary
PHP's OpenSSL stream peer verification checks the certificate's subjectAltName entries first and falls back to the Common Name if no SAN matches. RFC 6125 mandates ignoring the CN once any service identity is presented in the certificate. However, PHP incorrectly accepts certificates with a non-matching DNS SAN if the CN matches the requested peer name. This improper validation (CWE-297) can lead to impersonation attacks where a certificate trusted for one domain is used for another.
Potential Impact
An attacker with a certificate trusted by the client for one domain can impersonate another domain due to improper certificate validation. This could lead to partial confidentiality loss (CVSS impact: Confidentiality Low) but does not affect integrity or availability. The attack vector is adjacent network (AV:A), requiring low attack complexity and no privileges or user interaction.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided at this time. Users should monitor PHP Group advisories for updates and apply official patches once available.
CVE-2026-91769: CWE-297 Improper validation of certificate with host mismatch in PHP Group PHP
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.
CVSS v3.1
Score 4.3medium
Affected software
PHP Group
PHP
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
PHP's OpenSSL stream peer verification checks the certificate's subjectAltName entries first and falls back to the Common Name if no SAN matches. RFC 6125 mandates ignoring the CN once any service identity is presented in the certificate. However, PHP incorrectly accepts certificates with a non-matching DNS SAN if the CN matches the requested peer name. This improper validation (CWE-297) can lead to impersonation attacks where a certificate trusted for one domain is used for another.
Potential Impact
An attacker with a certificate trusted by the client for one domain can impersonate another domain due to improper certificate validation. This could lead to partial confidentiality loss (CVSS impact: Confidentiality Low) but does not affect integrity or availability. The attack vector is adjacent network (AV:A), requiring low attack complexity and no privileges or user interaction.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided at this time. Users should monitor PHP Group advisories for updates and apply official patches once available.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- php
- Date Reserved
- 2026-09-15T00:44:10.816Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ab6e198f7a7c5410648d4d0
Added to database: 09/25/2026, 21:03:20 UTC
Last enriched: 09/25/2026, 21:17:59 UTC
Last updated: 09/26/2026, 03:46:43 UTC
Views: 9
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