🛡️ CVE-2026-13577

🟠 CVSS 8.2 — High ✅ No Known Exploit CWE-338 NVD
8.2
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity none, availability high.

Weakness class

CVE-2026-13577 is classified as CWE-338: Use of Cryptographically Weak PRNG. A general-purpose random number generator is used where a cryptographic one is required.

Affected software

CVE-2026-13577 is recorded against 1 package.

  • unknown

Timeline and source

Published on 20 July 2026 and last revised on 22 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com
www.cve.org

Details

Severity HIGH
CVSS Score 8.2
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
CWE CWE-338
Public Exploit ✅ No
Source NVD
Published 2026-07-20
Updated 2026-08-11
Modified 2026-07-22
Fix URL N/A

Affected Packages

Software From version Fixed in
unknown — —

Similar Threats

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