CVE-2026-45067 Symfony: Email Header / SMTP Command Injection via CRLF in Symfony\Component\Mime\Address
Attackers can inject SMTP commands or email headers via CRLF in Symfony Mailer addresses, potentially executing code or modifying messages.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-45067?
CVE-2026-45067 is a medium-severity command injection vulnerability in symfony, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-93
Which versions are affected by CVE-2026-45067?
16 open source packages ship an affected version, including symfony/mime and symfony/symfony.
| Package | Affected | Fixed in |
|---|---|---|
symfony/mime Packagist | All versions | 5.4.52 |
symfony/mime Packagist | All versions | 5.4.52 |
symfony/mime Packagist | From 6.0.0 | 6.4.40 |
symfony/mime Packagist | From 6.0.0 | 6.4.40 |
symfony/mime Packagist | From 7.0.0 | 7.4.12 |
symfony/mime Packagist | From 7.0.0 | 7.4.12 |
10 more packages
symfony/mime Packagist | From 8.0.0 | 8.0.12 |
symfony/mime Packagist | From 8.0.0 | 8.0.12 |
symfony/symfony Packagist | All versions | 5.4.52 |
symfony/symfony Packagist | All versions | 5.4.52 |
symfony/symfony Packagist | From 6.0.0 | 6.4.40 |
symfony/symfony Packagist | From 6.0.0 | 6.4.40 |
symfony/symfony Packagist | From 7.0.0 | 7.4.12 |
symfony/symfony Packagist | From 7.0.0 | 7.4.12 |
symfony/symfony Packagist | From 8.0.0 | 8.0.12 |
symfony/symfony Packagist | From 8.0.0 | 8.0.12 |
How do I fix CVE-2026-45067?
Upgrade symfony/mime to a fixed version for your release line: 5.4.52, 6.4.40, 7.4.12 or 8.0.12.
Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.
Is CVE-2026-45067 being exploited?
There is no known exploitation of CVE-2026-45067 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as CLSA-2026-1782781183, DEBIAN-CVE-2026-45067, GHSA-qpmx-3rfj-7rhv, UBUNTU-CVE-2026-45067.