Symfony has Email Header / SMTP Command Injection via CRLF in Symfony\Component\Mime\Address

MOYENNE 6.3CVE-2026-45067 · GHSA-qpmx-3rfj-7rhv · Published 14/07/2026 · updated 14/07/2026

En bref

CVE-2026-45067 est une vulnérabilité MOYENNE (CVSS 6.3) touchant symfony/mime, symfony/symfony.
Probabilité d'exploitation dans les 30 prochains jours (EPSS) : 0.60%, plus élevée que 48.6% des vulnérabilités.
Correctif : mettre à jour vers 6.4.40, 7.4.12, 8.0.12, 5.4.52 ou plus récent.

Package	Affected versions	Patched versions
symfony/mime Packagist	`≥ 6.0.0, < 6.4.40≥ 7.0.0, < 7.4.12≥ 8.0.0, < 8.0.12< 5.4.52`	`6.4.407.4.128.0.125.4.52`
symfony/symfony Packagist	`≥ 6.0.0, < 6.4.40≥ 7.0.0, < 7.4.12≥ 8.0.0, < 8.0.12< 5.4.52`	`6.4.407.4.128.0.125.4.52`

Description

Symfony\Component\Mime\Address is the value-object every Symfony Mailer address (to/cc/bcc/from/reply-to) flows through; its constructor is documented as validating the address and throwing on invalid input, so developers treat it as a security boundary.

The constructor accepts email addresses whose local-part (the part before @) is an RFC-5322 quoted string containing raw \r\n bytes, e.g. "x\r\nBcc: attacker@evil"@example.com. The stored address is later emitted verbatim into (1) the rendered message headers and (2) SmtpTransport's MAIL FROM:<...> / RCPT TO:<...> protocol lines, turning the embedded CRLF into a new mail header and/or a new SMTP command.

Resolution

The Address constructor now rejects addresses containing line breaks.

The patch for this issue is available here for branch 5.4.

Credits

We would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.

NVD description

### Description `Symfony\Component\Mime\Address` is the value-object every Symfony Mailer address (to/cc/bcc/from/reply-to) flows through; its constructor is documented as validating the address and throwing on invalid input, so developers treat it as a security boundary. The constructor accepts email addresses whose local-part (the part before `@`) is an RFC-5322 *quoted string* containing raw `\r\n` bytes — e.g. `"x\r\nBcc: attacker@evil"@example.com`. The stored address is later emitted verbatim into (1) the rendered message headers and (2) `SmtpTransport`'s `MAIL FROM:<...>` / `RCPT TO:<...>` protocol lines, turning the embedded CRLF into a new mail header and/or a new SMTP command. ### Resolution The `Address` constructor now rejects addresses containing line breaks. The patch for this issue is available [here](https://github.com/symfony/symfony/commit/dc2dbd29211eb4ddc451373fa1374fb926e94604) for branch 5.4. ### Credits We would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.