The jumpUrl mechanism in class.tslib_fe.php in TYPO3 3.3.x through 3.8.x, 4.0 before 4.0.12, 4.1 before 4.1.10, 4.2 before 4.2.6, and 4.3alpha1 leaks a hash secret (juHash) in an error message, which allows remote attackers to read arbitrary files by including the hash in a request.