CVE-2026-45067CWE-93

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

Medium · published July 14, 2026

CVSS v4.0
6.3
EPSS
1%
Percentile
47.9
In the wild
Unconfirmed
What it is

### 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.

The record
Technical detail
CVSS v4.0
6.3 · MEDIUM
Vector
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
EPSS
0.00598 · 47.9th percentile
Weakness
CWE-93 · Improper Neutralization of CRLF Sequences ('CRLF Injection')
Published
2026-07-14T17:41Z
EPSS history
Timeline
  • 14 JUL 17:41Z
    Symfony: Email Header / SMTP Command Injection via CRLF in Symfony\Component\Mime\Address
    cvelistv5