All 2.0.X, 2.1.X, 2.2.X, 2.3.X, 2.4.X, and 2.5.X versions of the Symfony HttpFoundation component are affected by this security issue.
This issue has been fixed in Symfony 2.3.19, 2.4.9, and 2.5.4. Note that no fixes are provided for Symfony 2.0, 2.1, and 2.2 as they are not maintained anymore.
When an application uses an HTTP basic or digest authentication, Symfony does not parse the Authorization header properly, which could be exploited in some server setups (no exploits have been demonstrated though.)
The parsing of the Authorization header has been fixed to comply to the HTTP specification.
The patch for this issue is available here: https://github.com/symfony/symfony/pull/11829
I would like to thank Damien Tournoud for reporting this security issue and providing the initial patch and Christophe Coevoet for reviewing the patch.