There is a potential RCE with regards to Storable. We have added session ID validation to the session engine so that session backends based on Storable can reject malformed session IDs that may lead to exploitation of the RCE.

• https://metacpan.org/changes/distribution/Dancer2
• http://lists.preshweb.co.uk/pipermail/dancer-users/2018-April/005952.html
• https://github.com/PerlDancer/Dancer2/commit/3580f5d0874a9abf5483528f73bda9a7fd9ec7f1

Dancer2 versions through 2.1.0 for Perl generate insecure session ids when required CSPRNG modules are unavailable. Dancer2::Core::Role::SessionFactory::generate_id silently falls back to a built-in rand-derived session id unless both Math::Random::ISAAC::XS and Crypt::URandom are available. The fallback session id is generated from a SHA-1 hash of a call to the built-in rand function, the absolute path of the Dancer2::Core::Role::SessionFactory module, an internal counter, the process id, the module instance memory address, and a shuffled string of characters (using the List::Util::shuffle function, which also uses the built-in rand function). These are all low-entropy and easily guessed sources. The built-in rand() function is seeded with 32-bits and considered unsuitable for security applications. Predictable session ids could allow an attacker to gain access to systems.

• https://github.com/PerlDancer/Dancer2/blob/v2.1.0/lib/Dancer2/Core/Role/SessionFactory.pm#L142
• https://www.cve.org/CVERecord?id=CVE-2026-5080