CVE-2025-40926 Plack::Middleware::Session::Simple versions before 0.05 for Perl generates session ids insecurely
Insecure session ID generation allows attackers to predict IDs and hijack user sessions in Perl applications using this middleware.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-40926?
CVE-2025-40926 is a critical vulnerability in KAZEBURO Plack::Middleware::Session::Simple, published on 5 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2025-40926?
It affects 1 product.
Products include Kazeburo Plack\.
How do I fix CVE-2025-40926?
No fix has been published for CVE-2025-40926 yet. Limit exposure of the affected software until one is available.
Is CVE-2025-40926 being exploited?
There is no known exploitation of CVE-2025-40926 in the wild and no public exploit code.
Sources
Also known as GHSA-g98h-c5v8-8m3f.