CVE-2025-40926 PUBLISHED

Plack::Middleware::Session::Simple versions through 0.04 for Perl generates session ids insecurely.

The default session id generator returns a SHA-1 hash seeded with the built-in rand function, the epoch time, and the PID. 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.

Plack::Middleware::Session::Simple is intended to be compatible with Plack::Middleware::Session, which had a similar security issue CVE-2025-40923.

Users are advised to change the sid_generator attribute of Plack::Middleware::Session::Simple to a function that returns a securely generated session id based on a secure source of entropy from the system.

Users may consider using Plack::Middleware::Session version 0.35 or later.

• https://metacpan.org/release/KAZEBURO/Plack-Middleware-Session-Simple-0.04/source/lib/Plack/Middleware/Session/Simple.pm#L43
• https://github.com/kazeburo/Plack-Middleware-Session-Simple/pull/4
• https://github.com/kazeburo/Plack-Middleware-Session-Simple/commit/760bb358b8f53e52cf415888a4ac858fd99bb24e.patch
• https://www.cve.org/CVERecord?id=CVE-2025-40923
• https://security.metacpan.org/docs/guides/random-data-for-security.html

• CWE-340 Generation of Predictable Numbers or Identifiers CWE
• CWE-338 Use of Cryptographically Weak Pseudo-Random Number Generator CWE