A regular expression based DoS vulnerability in Action Dispatch <6.0.6.1,< 6.1.7.1, and <7.0.4.1. Specially crafted cookies, in combination with a specially crafted X_FORWARDED_HOST header can cause the regular expression engine to enter a state of catastrophic backtracking. This can cause the process to use large amounts of CPU and memory, leading to a possible DoS vulnerability All users running an affected release should either upgrade or use one of the workarounds immediately.