FrankenPHP is a modern application server for PHP. Prior to 1.11.2, when running FrankenPHP in worker mode, the $_SESSION superglobal is not correctly reset between requests. This allows a subsequent request processed by the same worker to access the $_SESSION data of the previous request (potentially belonging to a different user) before session_start() is called. This vulnerability is fixed in 1.11.2.
CWE-269, CWE-384, CWE-613