CVE-2026-45067

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CRLF Injection in Symfony Mailer Address Component

Publication date: 2026-07-14

Last updated on: 2026-07-14

Assigner: GitHub, Inc.

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-07-14

Last Modified

2026-07-14

Generated

2026-08-04

AI Q&A

2026-07-15

EPSS Evaluated

2026-08-02

NVD

CVE-2026-45067

EUVD

EUVD-2026-44322

Affected Vendors & Products

Vendor	Product	Version / Range
symfony	symfony	to 5.4.52 (exc)
symfony	symfony	to 6.4.40 (exc)
symfony	symfony	to 7.4.12 (exc)
symfony	symfony	to 8.0.12 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-93	The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.

Attack-Flow Graph

Executive Summary

This vulnerability in Symfony's Mime component allows attackers to inject malicious headers or SMTP commands by exploiting CRLF sequences in email addresses. The Address constructor incorrectly accepted email addresses with raw line breaks in the local-part, such as 'x Bcc: attacker@evil'@example.com. When processed, these line breaks split the address into separate headers or SMTP commands, enabling injection attacks.

Detection Guidance

Check Symfony Mailer logs for malformed email addresses containing CRLF sequences. Use grep to search for patterns like \r\n in email headers or SMTP commands. Example: grep -r 'Bcc:' /var/log/mail.log or grep -r '\r\n' /var/log/symfony.log.

Impact Analysis

Attackers could use this to send unauthorized emails from your domain, bypass security controls, or manipulate email headers. If your application uses Symfony Mailer with unpatched versions, malicious actors might inject additional recipients, alter message content, or spoof sender addresses in emails sent by your system.

Compliance Impact

This vulnerability could lead to unauthorized data exposure or manipulation, violating GDPR's integrity and confidentiality principles or HIPAA's security requirements for protected health information. Organizations using vulnerable Symfony versions may fail compliance audits.

Mitigation Strategies

Update Symfony to the latest patched version (5.4.52, 6.4.40, 7.4.12, or 8.0.12). If immediate update is not possible, implement input validation to reject email addresses with control characters or line breaks before they reach the Address constructor.

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