CVE-2025-40923: Miyagawa Plack::middleware::session

High severity, CVSS 7.3. EPSS: 0.4% chance of exploitation in the next 30 days.

Plack-Middleware-Session before version 0.35 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.

Affected products

• Miyagawa Plack::middleware::session: from 0.01, before 0.35 (fixed in 0.35)

Published 2025-07-16. Last modified 2026-06-17.