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🛡️ CVE-2026-45067 — mime

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-93 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. Rated impact: confidentiality none, integrity high, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Attack requirements: None — no deployment-specific condition has to hold.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Confidentiality impact: None.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: None.

Weakness class

CVE-2026-45067 is classified as CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection'). 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.

Affected software

CVE-2026-45067 is recorded against 3 packages.

  • symfony/mime (from 8.0.0 up to 8.0.12)
  • symfony/symfony (from 8.0.0 up to 8.0.12)
  • unknown

Timeline and source

Published on 27 May 2026 and last revised on 9 June 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
github.com (Web)
github.com (Web)
github.com (Web)
github.com (Package)
symfony.com (Web)

Other advisories for this package

symfony/mime has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection')) in other software:

CVE-2026-45067 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
CWE CWE-93
Public Exploit ✅ No
Source NVD
Published 2026-05-27
Updated 2026-08-20
Modified 2026-06-09
Fix URL N/A

Affected Packages

Software From version Fixed in
symfony/mime 8.0.0 8.0.12
symfony/symfony 8.0.0 8.0.12
unknown — —

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