CVE WatchJul 22, 2026

CVE-2026-13577

Dancer2 versions through 2.1.0 for Perl generate insecure session ids when required CSPRNG modules are unavailable. Dancer2::Core::Role::Se

CVSS

8.2

High

EPSS

0.5%

p38

KEV

—

Exploit Today

0-100

Published: Jul 20, 2026 · Last modified: Jul 22, 2026 · CWE-338 · CWE-340

EPSS · 30d

0.3%EPSS · 30 days0.5%

2026-08-122026-09-09

Technical description

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.

Official references

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