{"id":"CVE-2026-45063","aliases":["GHSA-ph86-p8f6-f9r2"],"url":"https://o3.security/vulnerability/CVE-2026-45063","summary":"Symfony: Identity Spoofing via Unanchored DN Regex in X509Authenticator","details":"### Description\n\n`X509Authenticator` implements client-certificate (mTLS) authentication: the web server validates the client's certificate against a trusted CA, then passes the certificate's Subject DN (Distinguished Name: a string like `CN=Alice,O=Example,emailAddress=alice@example.com`) to Symfony via `$_SERVER['SSL_CLIENT_S_DN']`. Symfony extracts the user identifier from that string.\n\nThe extraction uses an **unanchored** regex that matches `emailAddress=` anywhere in the DN string: including inside the *value* of a different RDN (Relative Distinguished Name: one `key=value` component of the DN), such as `CN`. An attacker who can obtain a certificate from a trusted CA with a free-text `CN` can smuggle `emailAddress=victim@target` inside the CN value and be authenticated as the victim.\n\n### Resolution\n\nThe `X509Authenticator` now uses a regex that anchors the match to an RDN boundary (start of string, or following a `,` / `/` separator).\n\nThe patch for this issue is available [here](https://github.com/symfony/symfony/commit/ccb3f724c7ff55670a6fe3521c7bf1514cceb478) for branch 5.4.\n\n### Credits\n\nSymfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.","published":"2026-07-14T18:28:22.074Z","modified":"2026-08-12T03:51:45.766195576Z","cvss":null,"epss":{"score":0.00367,"percentile":0.30317,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"symfony/security-http","fixedVersion":"5.4.52"},{"ecosystem":"Packagist","name":"symfony/security-http","fixedVersion":"6.4.40"},{"ecosystem":"Packagist","name":"symfony/security-http","fixedVersion":"7.4.12"},{"ecosystem":"Packagist","name":"symfony/security-http","fixedVersion":"8.0.12"},{"ecosystem":"Packagist","name":"symfony/symfony","fixedVersion":"5.4.52"},{"ecosystem":"Packagist","name":"symfony/symfony","fixedVersion":"6.4.40"},{"ecosystem":"Packagist","name":"symfony/symfony","fixedVersion":"7.4.12"},{"ecosystem":"Packagist","name":"symfony/symfony","fixedVersion":"8.0.12"}],"fix":{"url":"https://github.com/symfony/symfony/commit/59ef484029601a7af06f5e06c6ed921fdcea5a0d","label":"symfony/symfony@59ef484"},"references":[{"type":"WEB","url":"https://github.com/symfony/symfony/releases/tag/v5.4.52"},{"type":"WEB","url":"https://github.com/symfony/symfony/releases/tag/v6.4.40"},{"type":"WEB","url":"https://github.com/symfony/symfony/releases/tag/v7.4.12"},{"type":"WEB","url":"https://github.com/symfony/symfony/releases/tag/v8.0.12"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45063.json"},{"type":"ADVISORY","url":"https://github.com/symfony/symfony/security/advisories/GHSA-ph86-p8f6-f9r2"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-45063"},{"type":"FIX","url":"https://github.com/symfony/symfony/commit/59ef484029601a7af06f5e06c6ed921fdcea5a0d"},{"type":"WEB","url":"https://github.com/symfony/symfony/commit/ccb3f724c7ff55670a6fe3521c7bf1514cceb478"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security-http/CVE-2026-45063.yaml"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45063.yaml"},{"type":"PACKAGE","url":"https://github.com/symfony/symfony"},{"type":"WEB","url":"https://symfony.com/cve-2026-45063"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:45.766195576Z"}}