CVE-2026-45067

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

Published Jul 14, 2026 CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Debian DSA Debian DSA DSA-6312-1 symfony security update
Debian DSA Debian DSA DSA-6317-1 symfony security update
Github GHSA Github GHSA GHSA-qpmx-3rfj-7rhv Symfony has Email Header / SMTP Command Injection via CRLF in Symfony\Component\Mime\Address
History
Type Values Removed Values Added
First Time appeared Symfony
Symfony symfony
Vendors & Products Symfony
Symfony symfony
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Symfony: Email Header / SMTP Command Injection via CRLF in Symfony\Component\Mime\Address
Weaknesses CWE-93
References
Metrics cvssV4_0

{'score': 6.3, '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 14, 2026, 6:15 PM
Reserved
May 8, 2026, 6:45 PM
Status
Awaiting Analysis
Published
Jul 14, 2026, 6:17 PM
Modified
Jul 14, 2026, 8:25 PM