Vulnerability · Published Mar 5, 2026 · Assigned by CPANSec
CVE-2025-40926Plack::Middleware::Session::Simple versions before 0.05 for Perl generates session ids insecurely
Critical 9.8
In plain English
A critical-severity security flaw in Plack::Middleware::Session::Simple from KAZEBURO. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| KAZEBURO | Plack::Middleware::Session::Simple | 0 – before 0.05 |
Weakness: CWE-340, CWE-338 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://metacpan.org/release/KAZEBURO/Plack-Middleware-Session-Simple-0.04/source/lib/Plack/Middleware/Session/Simple.pm#L43
- https://github.com/kazeburo/Plack-Middleware-Session-Simple/pull/4 issue-tracking
- https://github.com/kazeburo/Plack-Middleware-Session-Simple/commit/760bb358b8f53e52cf415888a4ac858fd99bb24e.patch patch
- https://www.cve.org/CVERecord?id=CVE-2025-40923 vendor-advisory, related, vdb-entry
- https://security.metacpan.org/docs/guides/random-data-for-security.html technical-description
- https://metacpan.org/release/KAZEBURO/Plack-Middleware-Session-Simple-0.05/changes release-notes