Symfony has Email Header Injection via Non-Token Characters in Mime Parameter Names

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

4.9 · 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/E:U · score source

EPSS

• CVE-2026-45070: 0.39% estimated exploitation activity in the next 30 days; percentile 33.24 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Description Symfony\Component\Mime\Header\ParameterizedHeader (and the related parameter handling reachable from Symfony\Component\Mime\Header\Headers) is responsible for serializing structured headers such as Content-Type and Content-Disposition, which carry key=value parameters (e.g. Content-Disposition: attachment; filename="x"). RFC 2045 / RFC 5322 require parameter names to be tokens: a restricted ASCII subset that excludes whitespace, CR/LF, and the tspecials set. Symfony's parameter handling validates and properly encodes parameter values, but does not validate parameter names: the supplied name is emitted verbatim into the serialized header. A caller that derives a parameter name from untrusted input, e.g. an application that lets a user influence a Content-Disposition parameter name, can include \r\n or other non-token bytes inside the name, terminating the current header and injecting additional headers in the rendered message. This is the classic CRLF / header-injection…

Published by the source

27 May 2026, 21:09 UTC

Last modified by the source

27 May 2026, 21:09 UTC

Source last checked

26 Oct 2026, 14:40 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-vqc8-7275-q272

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# Patch Next advisory brief: CVE-2026-45070

Advisory: Symfony has Email Header Injection via Non-Token Characters in Mime Parameter Names
IDs: CVE-2026-45070, GHSA-vqc8-7275-q272
Record: https://patchnext.com/advisories/cve-2026-45070 (revision 1, source checked 26 Oct 2026, 14:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: symfony/mime 8.0.12, 7.4.12, 6.4.40, 5.4.52; symfony/symfony 8.0.12, 7.4.12, 6.4.40, 5.4.52. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist symfony/mime: affected < 5.4.52; >= 6.0.0, < 6.4.40; >= 7.0.0, < 7.4.12; >= 8.0.0, < 8.0.12; fixed in 8.0.12, 7.4.12, 6.4.40, 5.4.52
- Packagist symfony/symfony: affected < 5.4.52; >= 6.0.0, < 6.4.40; >= 7.0.0, < 7.4.12; >= 8.0.0, < 8.0.12; fixed in 8.0.12, 7.4.12, 6.4.40, 5.4.52

## Suggested inspection (read-only)
- Packagist symfony/mime: check the installed version with your package manager.
- Packagist symfony/symfony: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on symfony/mime, symfony/symfony.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-vqc8-7275-q272 (GitHub-reviewed advisory GHSA-vqc8-7275-q272 lists affected ranges: Packagist symfony/mime >=0 =6.0.0 =7.0.0 =8.0.0 =0 =6.0.0 =7.0.0 =8.0.0 <8.0.12)

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