CVE-2026-45070: Symfony Mime CRLF injection in ParameterizedHeader

CVE-2026-45070 · Severity: medium · CVSS 4 · Published 2026-07-14

Symfony is a popular PHP framework used to build web applications. A vulnerability in its email handling component could allow an attacker to inject malicious headers into outgoing emails if the application uses untrusted input to name email parameters. This could be used to bypass security filters, redirect replies, or perform other email-based attacks, potentially damaging a company's reputation or facilitating phishing.

Technologies: symfony/mime (Packagist), symfony/symfony (Packagist), Symfony Mime. Vendors: Packagist, Symfony.

Quick answers

Is CVE-2026-45070 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-45070 being exploited in the wild.
How severe is CVE-2026-45070?
Medium severity, with a CVSS score of 4, published 14 July 2026.
Which products and versions are affected?
symfony/mime (Packagist) ECOSYSTEM:introduced=0,fixed=5.4.52; symfony/symfony (Packagist) ECOSYSTEM:introduced=0,fixed=5.4.52; Symfony Mime < 5.4.52, >= 6.0.0 < 6.4.40, >= 7.0.0 < 7.4.12, >= 8.0.0 < 8.0.12, < 5.4.52, >= 6.0.0-BETA1 < 6.4.40, >= 7.0.0-BETA1 < 7.4.12, >= 8.0.0-BETA1 < 8.0.12.
Is there a fix for CVE-2026-45070?
Yes. symfony/mime (Packagist): upgrade to 5.4.52 or later; symfony/symfony (Packagist): upgrade to 5.4.52 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-45070 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-45070?
Check whether you run symfony/mime (Packagist), symfony/symfony (Packagist) or Symfony Mime at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • symfony/mime (Packagist): upgrade to 5.4.52 or later
    composer require symfony/mime:^5.4.52
  • symfony/symfony (Packagist): upgrade to 5.4.52 or later
    composer require symfony/symfony:^5.4.52

Technical details

A CRLF injection vulnerability exists in the Symfony\Component\Mime\Header\ParameterizedHeader class. While the component validates and encodes parameter values, it fails to sanitize parameter names, emitting them verbatim in the rendered mail headers. If an application derives a parameter name from untrusted user input, an attacker can include CRLF sequences or other non-token bytes to inject additional, arbitrary headers into structured mail headers like Content-Type or Content-Disposition. This is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12 by rejecting parameter names containing non-token characters.

Affected products

  • Symfony symfony/symfony < 5.4.52, >= 6.0.0-BETA1 < 6.4.40, >= 7.0.0-BETA1 < 7.4.12, >= 8.0.0-BETA1 < 8.0.12
  • Symfony symfony/mime < 5.4.52, >= 6.0.0-BETA1 < 6.4.40, >= 7.0.0-BETA1 < 7.4.12, >= 8.0.0-BETA1 < 8.0.12

Identifiers

  • CVE-2026-45070
  • GHSA-vqc8-7275-q272

Timeline

  • 2026-07-14: advisory: NVD publication date
  • 2026-05-20: patched: Release of fixed versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12

References

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