A HIGH-severity vulnerability identified as CVE-2026-13577 has been published on July 20, 2026 with a CVSS base score of 8.2. This security advisory provides a detailed breakdown of the vulnerability, its potential impact, weakness classification, and actionable steps to protect your systems.
Vulnerability Details
CVE ID: CVE-2026-13577
Severity: HIGH
CVSS Score: 8.2
Published: July 20, 2026
Weakness (CWE): CWE-338
| Attack Vector | Network |
| Attack Complexity | Low |
| Privileges Required | None |
| User Interaction | None |
| Confidentiality Impact | Low |
| Integrity Impact | None |
| Availability Impact | High |
Technical 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.
Potential Impact
If exploited, this high-severity vulnerability could allow an attacker to cause a denial of service. Organizations running affected software should treat this as a priority remediation item.
Recommended Action
No official patch is available yet. Until one is released:
- Monitor the official NVD page and vendor channels for patch announcements.
- Restrict access to the affected system or service where possible.
- Apply network-level mitigations such as firewall rules or WAF policies.
- Enable logging and alerting for anomalous activity related to this vulnerability.
- Review your incident response plan in case of active exploitation.
References
Related Security Advisories
- [HIGH] CVE-2026-13741 — CVSS 8.8 (July 16, 2026) — HIGH / CVSS 8.8
- [HIGH] CVE-2026-15804 — CVSS 8.8 (July 15, 2026) — HIGH / CVSS 8.8
- [HIGH] CVE-2026-15583 — CVSS 8.6 (July 15, 2026) — HIGH / CVSS 8.6
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