========================================================================
CVE-2025-40926                                       CPAN Security Group
========================================================================

         CVE ID:  CVE-2025-40926
   Distribution:  Plack-Middleware-Session-Simple
       Versions:  through 0.04

       MetaCPAN:
https://metacpan.org/dist/Plack-Middleware-Session-Simple
       VCS Repo:
https://github.com/kazeburo/Plack-Middleware-Session-Simple

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

Description
-----------
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.

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

Workarounds
-----------
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.

References
----------
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