CVE-2026-5081
CRITICALDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 23% of all known CVEs.
References
Related Vulnerabilities
Other CWE-340 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2026-11374 | Critical | 9.0 | 2.0% | - | - |
| CVE-2024-47945 | Critical | 9.8 | 0.9% | - | Fix |
| CVE-2024-28957 | Medium | 5.3 | 0.8% | - | - |
| CVE-2020-1905 | Low | 3.3 | 0.6% | - | Fix |
| CVE-2025-40931 | Critical | 9.1 | 0.6% | - | - |
| CVE-2026-3256 | Critical | 9.8 | 0.5% | - | - |
Common questions
How do I fix CVE-2026-5081?
No published fix for CVE-2026-5081 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-5081 being actively exploited?
Not that we know of. CVE-2026-5081 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.30% is the estimated probability that it will be exploited in the next 30 days. That is higher than 23% of all scored CVEs.
How severe is CVE-2026-5081?
CVE-2026-5081 has a CVSS v3 base score of 9.1, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-15.