HTTP::Session versions before 0.54 for Perl contain a vulnerability in the HTTP::Session::Store::CHI module that allows memcached command injection via unfiltered session IDs. The session ID from the client's cookie is passed unchanged to the CHI cache, which does not validate or escape keys for memcached drivers. This allows an attacker to inject control characters (CR and LF) into the session ID, prematurely ending the cache command and causing the server to interpret subsequent bytes as additional commands.