CVE-2026-91769 (GCVE-0-2026-91769)

Vulnerability from cvelistv5 – Published: 2026-09-25 20:59 – Updated: 2026-09-25 20:59
VLAI
Title
TLS Hostname Verification Falls Back to CN After SAN Mismatch
Summary
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.
Severity
4.3 (Medium)
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CWE
  • CWE-297 - Improper validation of certificate with host mismatch
Assigner
References
Impacted products
Vendor Product Version CPE status
PHP Group PHP Affected: 8.2.* , < 8.2.34 (semver)
Affected: 8.3.* , < 8.3.35 (semver)
Affected: 8.4.* , < 8.4.26 (semver)
Affected: 8.5.* , < 8.5.11 (semver)
guessed Create a notification for this product.
Credits
Cantina (https://www.cantina.security/) David Korczynski Jakub Zelenka Arnaud Le Blanc Alexandre Daubois
Show details on NVD website
To clipboard 

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              "status": "affected",
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          "value": "David Korczynski"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "Jakub Zelenka"
        },
        {
          "lang": "en",
          "type": "remediation reviewer",
          "value": "Arnaud Le Blanc"
        },
        {
          "lang": "en",
          "type": "remediation reviewer",
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        }
      ],
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              "value": "\u003cp\u003ePHP\u0027s OpenSSL stream peer verification checks the certificate\u0027s 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 \u003ccode\u003epeer_name\u003c/code\u003e. A certificate trusted by the client for one name can therefore be used to impersonate another.\u003c/p\u003e"
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        }
      ],
      "impacts": [
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            "attackVector": "ADJACENT_NETWORK",
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            "baseScore": 4.3,
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            "confidentialityImpact": "LOW",
            "integrityImpact": "NONE",
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              "description": "CWE-297 Improper validation of certificate with host mismatch",
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      "providerMetadata": {
        "dateUpdated": "2026-09-25T20:59:39.727Z",
        "orgId": "dd77f84a-d19a-4638-8c3d-a322d820ed2b",
        "shortName": "php"
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      "source": {
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      "title": "TLS Hostname Verification Falls Back to CN After SAN Mismatch",
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    "cveId": "CVE-2026-91769",
    "datePublished": "2026-09-25T20:59:39.727Z",
    "dateReserved": "2026-09-15T00:44:10.816Z",
    "dateUpdated": "2026-09-25T20:59:39.727Z",
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        "cveTags": [],
        "descriptions": [
          {
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            "value": "PHP\u0027s OpenSSL stream peer verification checks the certificate\u0027s 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."
          }
        ],
        "id": "CVE-2026-91769",
        "lastModified": "2026-09-25T21:17:24.913",
        "metrics": {
          "cvssMetricV31": [
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              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "ADJACENT_NETWORK",
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                "confidentialityImpact": "LOW",
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}



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