PAGI::Middleware::Session::Store::Cookie versions through 0.001003 for Perl generates random bytes insecurely. PAGI::Middleware::Session::Store::Cookie attempts to read bytes from the /dev/urandom device directly. If that fails (for example, on systems without the device, such as Windows), then it will emit a warning that recommends the user install Crypt::URandom, and then return a string of random bytes generated by the built-in rand function, which is unsuitable for cryptographic applications.

This modules does not use the Crypt::URandom module, and installing it will not fix the problem. The random bytes are used for generating an initialisation vector (IV) to encrypt the cookie. A predictable IV may make it easier for malicious users to decrypt and tamper with the session data that is stored in the cookie.