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Fencer Vulns
critical 9.1

CVE-2026-5081 json

Apache::Session::Generate::ModUniqueId versions from 1.54 through 1.94 for Perl session ids are insecure

published 2026-05-06 6 mo ago modified 2026-10-26 13 d ago also EUVD-2026-27823

cvss
9.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 23%
public exploits
0
none known

Summary

Apache::Session::Generate::ModUniqueId versions from 1.54 through 1.94 for Perl session ids are insecure.

Apache::Session::Generate::ModUniqueId (added in version 1.54) uses the value of the UNIQUE_ID environment variable for the session id. The UNIQUE_ID variable is set by the Apache mod_unique_id plugin, which generates unique ids for the request. The id is based on the IPv4 address, the process id, the epoch time, a 16-bit counter and a thread index, with no obfuscation.

The server IP is often available to the public, and if not available, can be guessed from previous session ids being issued. The process ids may also be guessed from previous session ids. The timestamp is easily guessed (and leaked in the HTTP Date response header).

The purpose of mod_unique_id is to assign a unique id to requests so that events can be correlated in different logs. The id is not designed, nor is it suitable for security purposes.

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-2026-5081 updated cvss 8.2

Apache::Session::Generate::ModUniqueId: Perl: mod_unique_id: Apache HTTP Server: Apache::Session::Generate::ModUniqueId: Session ID predictability allows unauthorized access

  • Red Hat Hardened Images perl 5.42.2-524.1.hum1
    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
yes
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CISA ADP 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
CNA 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Affected products

  • CHORNY Apache::Session::Generate::ModUniqueId
  • Red Hat Red Hat Hardened Images

Classification

Weakness
  • CWE-340 Generation of Predictable Numbers or Identifiers
  • CWE-341 Predictable from Observable State

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.