CVE-2026-45070 Symfony: Email Header Injection via Non-Token Characters in Mime Parameter Names

What is CVE-2026-45070?

CVE-2026-45070 is a medium-severity vulnerability in Sensiolabs Symfony, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 5.4.52, 6.4.40, 7.4.12, and 8.0.12, Symfony\Component\Mime\Header\ParameterizedHeader validates and encodes parameter values but emits parameter names verbatim, allowing a caller that derives a parameter name from untrusted input to include CRLF or other non-token bytes and inject additional headers into rendered structured mail headers such as Content-Type or Content-Disposition. This issue is reported as fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.

Weakness: CWE-93

Which versions are affected by CVE-2026-45070?

16 open source packages ship an affected version, including symfony/mime and symfony/symfony. It affects 1 product.

Products include Sensiolabs Symfony.

How do I fix CVE-2026-45070?

Upgrade symfony/mime to a fixed version for your release line: 5.4.52, 6.4.40, 7.4.12 or 8.0.12.

Is CVE-2026-45070 being exploited?

There is no known exploitation of CVE-2026-45070 in the wild and no public exploit code.

Other vulnerabilities in Sensiolabs Symfony

• CVE-2019-11325 Improper Input Validation in Symfony Critical 9.8
• CVE-2017-11365 Symfony Incorrect Access Control Critical 9.8
• CVE-2019-10913 Invalid HTTP method overrides allow possible XSS or other attacks in Symfony Critical 9.8
• CVE-2018-11407 Symfony Authentication Bypass Critical 9.8
• CVE-2016-2403 Symfony Authentication Bypass Critical 9.8

All Sensiolabs Symfony vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as CLSA-2026-1783386119, DEBIAN-CVE-2026-45070, GHSA-vqc8-7275-q272, UBUNTU-CVE-2026-45070.