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Fencer Vulns
high 7.3

CVE-2025-40923 json

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

published 2025-07-16 15 mo ago modified 2026-06-17 4 mo ago also EUVD-2025-21693

cvss
7.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 33%
public exploits
0
none known

Summary

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.

Patch / fix

  • MIYAGAWA Plack::Middleware::Session 0.35
  • libplack-middleware-session-perl Debian 14 0.36-1

debian advisories DEBIAN-CVE-2025-40923

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-40923 updated cvss 5.3

plack-middleware-session: Plack-Middleware-Session insecure session ids

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
15 mo ago

Exploit prediction

0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
CNA 3.1 7.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Affected products

  • MIYAGAWA Plack::Middleware::Session

Classification

Weakness
  • CWE-340 Generation of Predictable Numbers or Identifiers
  • CWE-338 Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.