CVE-2025-40923: Plack-Middleware-Session before version 0.35 for Perl generates session ids insecurely Robert Rothenberg 16 Jul 2025 13:06 UTC

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CVE-2025-40923                                       CPAN Security Group
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         CVE ID:  CVE-2025-40923
   Distribution:  Plack-Middleware-Session
       Versions:  from 0.01 before 0.35

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

Plack-Middleware-Session before version 0.35 for Perl generates session
ids insecurely

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

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

Workarounds
-----------
Users who are unable to upgrade are advised to change the sid_generator
attribute of Plack::Session::State to a function that returns a
securely generated session id based on a secure source of entropy from
the system.

Solutions
---------
Users are advised to upgrade to Plack-Middleware-Session v0.35 or
later.

References
----------
https://metacpan.org/release/MIYAGAWA/Plack-Middleware-Session-0.34/source/lib/Plack/Session/State.pm#L22
https://github.com/plack/Plack-Middleware-Session/pull/52
https://github.com/plack/Plack-Middleware-Session/commit/1fbfbb355e34e7f4b3906f66cf958cedadd2b9be.patch
https://security.metacpan.org/docs/guides/random-data-for-security.html