CVE-2020-5255

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.

• CWE-435
• CWE-20

• https://github.com/symfony/symfony/commit/dca343442e6a954f96a2609e7b4e9c21ed6d74e6Patch, Third Party Advisory
• https://github.com/symfony/symfony/security/advisories/GHSA-mcx4-f5f5-4859Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/C36JLPHUPKDFAX6D5WYFC4ALO2K7RDUQ/
• https://symfony.com/blog/cve-2020-5255-prevent-cache-poisoning-via-a-response-content-type-headerThird Party Advisory
• https://github.com/symfony/symfony/commit/dca343442e6a954f96a2609e7b4e9c21ed6d74e6Patch, Third Party Advisory
• https://github.com/symfony/symfony/security/advisories/GHSA-mcx4-f5f5-4859Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/C36JLPHUPKDFAX6D5WYFC4ALO2K7RDUQ/
• https://symfony.com/blog/cve-2020-5255-prevent-cache-poisoning-via-a-response-content-type-headerThird Party Advisory

Published

Mar 30, 2020

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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