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.
Advisories
Source ID Title
Debian DSA Debian DSA DSA-6514-1 php8.4 security update
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Fri, 25 Sep 2026 21:15:00 +0000

Type Values Removed Values Added
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.
Title TLS Hostname Verification Falls Back to CN After SAN Mismatch
Weaknesses CWE-297
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: php

Published:

Updated: 2026-09-25T20:59:39.727Z

Reserved: 2026-09-15T00:44:10.816Z

Link: CVE-2026-91769

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-25T21:17:24.913

Modified: 2026-09-25T21:17:24.913

Link: CVE-2026-91769

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-25T23:00:15Z

Weaknesses