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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
References 5
https://github.com/kazeburo/Plack-Middleware-Session-Simple/commit/760bb358b8f5…
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https://github.com/kazeburo/Plack-Middleware-Session-Simple/pull/4
9b29abf9-4ab0-4765-b253-1875cd9b441e
https://metacpan.org/release/KAZEBURO/Plack-Middleware-Session-Simple-0.04/sour…
9b29abf9-4ab0-4765-b253-1875cd9b441e
https://security.metacpan.org/docs/guides/random-data-for-security.html
9b29abf9-4ab0-4765-b253-1875cd9b441e
https://www.cve.org/CVERecord?id=CVE-2025-40923
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