CVE-2020-5255: Sensiolabs Symfony

Medium severity, CVSS 4.3. EPSS: 1.3% chance of exploitation in the next 30 days.

In Symfony before versions 4.4.7 and 5.0.7, when a `Response` does not contain a `Content-Type` header, affected versions of Symfony can fallback to the format defined in the `Accept` header of the request, leading to a possible mismatch between the response's content and `Content-Type` header. When the response is cached, this can prevent the use of the website by other users. This has been patched in versions 4.4.7 and 5.0.7.

Affected products

• Sensiolabs Symfony: from 4.4.0, before 4.4.7 (fixed in 4.4.7); from 5.0.0, before 5.0.7 (fixed in 5.0.7)

Published 2020-03-30. Last modified 2026-06-17.