Mojolicious versions from 7.28 through 9.39 for Perl may generate weak HMAC session secrets.
When creating a default app with the mojo generate app tool, a weak secret is written to the applications configuration file using the insecure rand() function, and used for authenticating and protecting the integrity of the applications sessions. This may allow an attacker to brute force the applications session keys.
The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG’s algorithm is not cryptographically strong.
When a non-cryptographic PRNG is used in a cryptographic context, it can expose the cryptography to certain types of attacks. Often a pseudo-random number generator (PRNG) is not designed for cryptography. Sometimes a mediocre source of randomness is sufficient or preferable for algorithms that use random numbers. Weak generators generally take less processing power and/or do not use the precious, finite, entropy sources on a system. While such PRNGs might have very useful features, these same features could be used to break the cryptography.