Threats affecting pkg:composer/symfony/security-http

Authentication bypass by spoofing in X509Authenticator and X509AuthenticationListener of Symfony versions prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11 allows an attacker holding a certificate from the application's trusted CA who can influence the CN to authenticate as an arbitrary user of the application, including a privileged one, following an incomplete fix for CVE-2026-45063. X509Authenticator extracts the user identifier from the Subject DN (Distinguished Name) that the web server passes in $_SERVER['SSL_CLIENT_S_DN']. The fix for CVE-2026-45063 anchored that extraction to an RDN (Relative Distinguished Name) boundary, but the regular expression used was not escape-aware. The expression runs against an already serialized DN, so it cannot tell an RDN separator from a separator character that occurs inside a value. Under RFC 2253, used by Apache and by nginx's $ssl_client_s_dn, a comma inside a value is escaped as \, and the expression reads it as a separator regardless. RFC 2253 also does not treat / as a separator, so it leaves it bare inside a value, while the expression treats every / as one. The legacy X509_NAME_oneline() format, used by Apache's LegacyDNStringFormat and by nginx's $ssl_client_s_dn_legacy, is the mirror image: it escapes / as \/ and leaves , bare. In that format, a certificate with no emailAddress attribute, or whose poisoned CN precedes it, authenticates as the smuggled address. To cover both RFC 2253 and the legacy X509_NAME_oneline() format, X509Authenticator and X509AuthenticationListener now split the DN into RDNs before looking for the attribute, instead of matching the attribute against the serialized string. They select the separator from the serialization, split on unescaped occurrences of that separator only, unescape each RDN afterwards with the rules of its format, and require the attribute to span a whole RDN. The accepted value grammar is unchanged. Applications that pass a per-attribute user key (such as SSL_CLIENT_S_DN_Email) and deployments whose CA generates or validates the subject are not affected by this vulnerability.

### Description Symfony's `#[IsGranted('...')]`, `#[IsSignatureValid]`, and `#[IsCsrfTokenValid(...)]` attributes allow you to define a `methods: [...]` argument to only enforce these checks for the listed HTTP methods and skip them otherwise. E.g. an attribute defining `methods: ['GET']` would be ignored for a `HEAD` request. On the other hand, Symfony's router (and HTTP semantics generally) serves `HEAD` requests using the `GET` handler. Therefore, a controller protected by e.g. `#[IsGranted('ROLE_ADMIN', methods: ['GET'])]` can be reached via `HEAD` with the authorization check silently skipped. Even if the `HEAD` request won't get any response content, response headers leak (`Content-Length`, `Location`, custom headers). Also, the controller still executes and any side effects (DB writes, state changes) occur. ### Resolution When adding `GET` in the `methods` option of these attributes, Symfony now also include the `HEAD` method automatically. The patch for this issue is available [here](https://github.com/symfony/symfony/commit/fa8d5c67aa4b22c9656e3fd7d5c3aa59865bf838) for branch 7.4. ### Credits Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and Alexandre Daubois for fixing it.