LowGHSA-mcx4-f5f5-4859BIT-symfony-2020-5255CVE-2020-5255

Prevent cache poisoning via a Response Content-Type header in Symfony

Published 30 Mar 2020 · Updated 10 Sept 2026

Affected packages

symfony/http-foundationComposer
Affected
>=4.4.0 <4.4.7
Fixed in
4.4.7
Update to the fixed version for your release line, for example:composer require symfony/http-foundation:^4.4.7
symfony/http-foundationComposer
Affected
>=5.0.0 <5.0.7
Fixed in
5.0.7
Update to the fixed version for your release line, for example:composer require symfony/http-foundation:^5.0.7
symfony/symfonyComposer
Affected
>=4.4.0 <4.4.7
Fixed in
4.4.7
Update to the fixed version for your release line, for example:composer require symfony/symfony:^4.4.7
symfony/symfonyComposer
Affected
>=5.0.0 <5.0.7
Fixed in
5.0.7
Update to the fixed version for your release line, for example:composer require symfony/symfony:^5.0.7

Details

Description -----------

When a Response does not contain a Content-Type header, Symfony falls back 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 lead to a corrupted cache where the cached format is not the right one.

Resolution ----------

Symfony does not use the Accept header anymore to guess the Content-Type.

The patch for this issue is available here for the 4.4 branch.

Credits -------

I would like to thank Xavier Lacot from JoliCode for reporting & Yonel Ceruto and Tobias Schultze for fixing the issue.

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References

Advisory data from OSV.dev (opens OSV.dev in a new tab), refreshed daily.