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9.8
Plack::Middleware::Session::Simple generates insecure session IDs for Perl
CVE-2025-40926
Summary
Plack::Middleware::Session::Simple for Perl generates session IDs in a way that makes them predictable, which could allow an attacker to access systems. This is a security risk because it's easy to guess or calculate the session ID. To fix this, update Plack::Middleware::Session::Simple to version 0.05 or later.
What to do
No fix is available yet. Check with your software vendor for updates.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| kazeburo | plack\ | \ | – |
Original title
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...
Original 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.
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.
nvd CVSS3.1
9.8
Vulnerability type
CWE-338
CWE-340
- https://github.com/kazeburo/Plack-Middleware-Session-Simple/commit/760bb358b8f53...
- https://github.com/kazeburo/Plack-Middleware-Session-Simple/pull/4
- https://metacpan.org/release/KAZEBURO/Plack-Middleware-Session-Simple-0.04/sourc...
- https://security.metacpan.org/docs/guides/random-data-for-security.html
- https://www.cve.org/CVERecord?id=CVE-2025-40923
- https://metacpan.org/release/KAZEBURO/Plack-Middleware-Session-Simple-0.05/chang...
Published: 5 Mar 2026 · Updated: 13 Mar 2026 · First seen: 6 Mar 2026