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🛡️ CVE-2026-45070 — symfony

🟡 CVSS 6.5 — Medium ✅ No Known Exploit CWE-93 NVD
6.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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

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 primitive applied to the parameter-name slot.

Resolution

ParameterizedHeader now rejects parameter names that contain bytes outside the RFC token character class.

The patch for this issue is available [here](https://github.com/symfony/symfony/commit/e62ea217f8b4ca8ae922ad0f949e0c4dc1f9b613) for branch 5.4.

Credits

Symfony would like to thank Fabian Fleischer for reporting the issue and Alexandre Daubois for fixing it.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity low, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: Low — limited, and the attacker does not choose what is affected.
  • Integrity impact: Low — limited, and the attacker does not choose what is affected.
  • Availability impact: None.

Weakness class

CVE-2026-45070 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-2026-45070 is recorded against 3 packages.

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

Timeline and source

Published on 14 July 2026 and last revised on 16 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
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Other advisories for this package

symfony 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-2026-45070 on other distributions

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

Details

Severity MEDIUM
CVSS Score 6.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
CWE CWE-93
Public Exploit ✅ No
Source NVD
Published 2026-07-14
Updated 2026-08-20
Modified 2026-07-16

Affected Packages

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

Similar Threats

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