CVE-2026-45067
Symfony: Email Header / SMTP Command Injection via CRLF in Symfony\Component\Mime\Address
- State
- Published
- Severity
- 6.3 Medium
- Published
- Jul 14, 2026
- Updated
- Jul 14, 2026
- Reserved
- May 8, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 6.3 Medium | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N | GitHub_M |
Weaknesses
- CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')
Affected Products
| Product | Versions |
|---|---|
symfonysymfony |
|
References
- https://github.com/symfony/symfony/security/advisories/GHSA-qpmx-3rfj-7rhv
- https://github.com/symfony/symfony/commit/a1c42cbe517bc146a54da7505a107ded317478fe
- https://github.com/symfony/symfony/releases/tag/v5.4.52
- https://github.com/symfony/symfony/releases/tag/v6.4.40
- https://github.com/symfony/symfony/releases/tag/v7.4.12
- https://github.com/symfony/symfony/releases/tag/v8.0.12
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