CVE-2026-13577
Deferred
Deferred - Pending Action
Predictable Session ID Generation in Dancer2
Vulnerability report for CVE-2026-13577, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-07-20
Last updated on: 2026-07-20
Assigner: CPANSec
Description
Description
Dancer2 versions through 2.1.0 for Perl generate insecure session ids when CSPRNG modules are unavailable.
Dancer2::Core::Role::SessionFactory::generate_id silently falls back to a built-in rand-derived session id when both Math::Random::ISAAC::XS and Crypt::URandom are unavailable.
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.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| perl_dancer | dancer2 | 2.1.0 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-340 | The product uses a scheme that generates numbers or identifiers that are more predictable than required. |
| CWE-338 | The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong. |
