Cover of the book Symfony 5: The Fast Track

Symfony 5: The Fast Track is the best book to learn modern Symfony development, from zero to production. +300 pages in full color showing how to combine Symfony with Docker, APIs, queues & async tasks, Webpack, Single-Page Applications, etc.

Buy printed version

CVE-2019-18887: Use constant time comparison in UriSigner

Affected versions

Symfony 2.8.0 to 2.8.51, 3.4.0 to 3.4.34, 4.2.0 to 4.2.11 and 4.3.0 to 4.3.7 versions of the Symfony HttpKernel component are affected by this security issue.

The issue has been fixed in Symfony 2.8.52, 3.4.35, 4.2.12 and 4.3.8.

Note that no fixes are provided for Symfony 3.0, 3.1, 3.2, 3.3, 4.0 and 4.1 as they are not maintained anymore.

This will be the last Symfony 2.8 security fix as it enters EOL; please upgrade to a more recent version of Symfony to continue receiving updates.


When checking the signature of an URI (an ESI fragment URL for instance), the URISigner did not used a constant time string comparison function, resulting in a potential remote timing attack vulnerability.


We now use PHP's built-in hash_equals() function to compare strings.

The patch for this issue is available here for branch 4.2.


I would like to thank Felix Sokoliuk for reporting & Christophe Coevoet for fixing the issue.

Manage your notification preferences to receive an email as soon as a Symfony security release is published.
If you have found a security issue in Symfony, please send the details to security [at] and don't disclose it publicly until we can provide a fix for it.

CVE-2019-18887: Use constant time comparison in UriSigner

Tweet this


Comments are closed.

To ensure that comments stay relevant, they are closed for old posts.