Catalyst::Plugin::Session before version 0.44 for Perl generates session ids insecurely. The session id is generated from a (usually SHA-1) hash of a simple counter, the epoch time, the built-in rand function, the PID and the current Catalyst context. This information is of low entropy. The PID will come from a small set of numbers, and the epoch time may be guessed, if it is not leaked from the HTTP Date header. The built-in rand function is unsuitable for cryptographic usage. Predicable session ids could allow an attacker to gain access to systems.