CVE-2025-40926CWE-338CWE-340

Plack::Middleware::Session::Simple versions before 0.05 for Perl generates session ids insecurely

Critical · published March 5, 2026

CVSS v3.1
9.8
EPSS
0%
Percentile
38.9
In the wild
Unconfirmed
What it is

Plack::Middleware::Session::Simple versions before 0.05 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.

Predictable 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.

The record
Technical detail
CVSS v3.1
9.8 · CRITICAL
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.00460 · 38.9th percentile
Weaknesses
CWE-338 · Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG); CWE-340 · Generation of Predictable Numbers or Identifiers
Published
2026-03-05T01:24Z
EPSS history
Timeline
  • 05 MAR 01:24Z
    Plack::Middleware::Session::Simple versions before 0.05 for Perl generates session ids insecurely
    cvelistv5