TLS Hostname Verification Falls Back to CN After SAN Mismatch

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-91769
StatePUBLISHED
Assignerphp
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-25 21:17:24 UTC
Updated2026-09-25 21:17:24 UTC
DescriptionPHP'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.

Risk And Classification

Primary CVSS: v3.1 4.3 MEDIUM from [email protected]

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Problem Types: CWE-297 | CWE-297 CWE-297 Improper validation of certificate with host mismatch

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.3MEDIUMCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
3.1CNACVSS4.3MEDIUMCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA PHP Group PHP affected 8.2.* 8.2.34 semver Not specified
CNA PHP Group PHP affected 8.3.* 8.3.35 semver Not specified
CNA PHP Group PHP affected 8.4.* 8.4.26 semver Not specified
CNA PHP Group PHP affected 8.5.* 8.5.11 semver Not specified

References

ReferenceSourceLinkTags
github.com/php/php-src/security/advisories/GHSA-vvx9-73fr-5jjx [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Cantina (https://www.cantina.security/) (en)

CNA: David Korczynski (en)

CNA: Jakub Zelenka (en)

CNA: Arnaud Le Blanc (en)

CNA: Alexandre Daubois (en)

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