CVE-2025-40926: KAZEBURO Plack::Middleware::Session::Simple · Generation of Predictable Numbers or Identifiers
Affects KAZEBURO Plack::Middleware::Session::SimpleSource CVE Database V5
Mentioned vulnerabilities
Not known to be exploited · CVSS 9.8 Critical : upgrade to 0.05 as a priority.
Data as of 30 Oct 2026, 11:52 UTC
Contested
Critical score, yet low EPSS after six months- EPSS
- 0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 0.05
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 5 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade Plack::Middleware::Session::Simple and Plack-Middleware-Session-Simple to 0.05.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| KAZEBUROPlack::Middleware::Session::Simple | Affected
| Fixed in
|
GitHubPlack-Middleware-Session-Simplepkg:github/Plack-Middleware-Session-SimpleOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
If you cannot patch yet, users should avoid using affected versions of Plack::Middleware::Session::Simple or implement alternative secure session ID generation methods that use cryptographically secure random number generators. Monitoring vendor channels for updates is recommended.
Description
CVE-2025-40926 is a critical vulnerability in Plack::Middleware::Session::Simple versions before 0.05 for Perl, where session IDs are generated using a predictable method. The default session ID generator uses a SHA-1 hash seeded with the built-in rand function, epoch time, and process ID (PID). Since the PID is from a small set of numbers and the epoch time can be guessed or leaked, the session IDs are predictable. This weakness can allow attackers to guess valid session IDs and potentially gain unauthorized access. The vulnerability has a CVSS score of 9.8, indicating a critical severity level.
References
- metacpan.org/release/KAZEBURO/Plack-Middleware-Session-Simple-0.04/source/lib/Plack/Middleware/Session/Simple.pm (opens in a new tab)
- github.com/kazeburo/Plack-Middleware-Session-Simple/pull/4 (opens in a new tab)
- github.com/kazeburo/Plack-Middleware-Session-Simple/commit/760bb358b8f53e52cf415888a4ac858fd99bb24e.patch (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-40923 (opens in a new tab)
- security.metacpan.org/docs/guides/random-data-for-security.html (opens in a new tab)
- metacpan.org/release/KAZEBURO/Plack-Middleware-Session-Simple-0.05/changes (opens in a new tab)