Affected Versions
2.3.19 - 2.3.28, 2.4.9 - 2.4.10, 2.5.4 - 2.5.11, 2.6.0 - 2.6.7 versions of the Symfony HttpKernel component are affected by this security issue.
This issue has been fixed in Symfony 2.3.29, 2.5.12, and 2.6.8. Note that no fixes are provided for Symfony 2.4 as it's not maintained anymore. Symfony 2.7 hasn't been released yet and the fix will be included in the first stable release.
Description
Applications with ESI or SSI support enabled, that use the
FragmentListener, are vulnerable to unauthorized access. A malicious user
can call any controller via the /_fragment path by providing an invalid
hash in the URL (or removing it), bypassing URL signing and security rules.
FragmentListener throws an AccessDeniedHttpException in case URL is not
signed correctly. However, the ExceptionListener triggers kernel events
again by making a sub-request. Since the FragmentListener does no signing
for sub-requests, the controller is called even though the original request was
forbidden. As a result the user receives a 403 response with content generated
by the controller.
Resolution
The fix implements a check in the FragmentListener so it is not called in
case a _controller attribute was previously set.
The patch for this issue is available here.
Credits
I would like to thank Jakub Zalas for reporting this security issue and providing a fix. Jakub also wrote the security advisory.
To clarify, your application is affected if esi support is enabled in your config.yml, but you haven't disabled the FragmentListener (framework -> fragments -> enabled: false).
I've just run security:check on v2.6.7 and got no results. Am I wrong in thinking this issue should pop up?
@Mac it has been fixed in v2.6.8 so v2.6.7 can not detect the issue.
After read again what does security:check, I think it should detect it.
PR to the security advisory was merged after this blog post was written (see https://github.com/FriendsOfPHP/security-advisories/pull/71). security:check detects this vulnerability now.