What’s Vulnerable › Vulnerabilities

CVE-2019-5420

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 89.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2019-03-27 · updated 2026-06-17
• Weakness: CWE-77

Description

A remote code execution vulnerability in development mode Rails <5.2.2.1, <6.0.0.beta3 can allow an attacker to guess the automatically generated development mode secret token. This secret token can be used in combination with other Rails internals to escalate to a remote code execution exploit.

Affected products

• Debian Linux: 8.0
• Fedoraproject Fedora: 30
• Ruby on Rails: before 5.2.2.1; 6.0.0-beta1, 6.0.0-beta2 — fixed in 5.2.2.1

How to fix

Upgrade to a fixed version: Ruby on Rails 5.2.2.1. Check the vendor advisory for mitigations.

References

• http://packetstormsecurity.com/files/152704/Ruby-On-Rails-DoubleTap-Development-Mode-secret_key_base-Remote-Code-Execution.html
• https://groups.google.com/forum/#%21topic/rubyonrails-security/IsQKvDqZdKw
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Y43636TH4D6T46IC6N2RQVJTRFJAAYGA/
• https://weblog.rubyonrails.org/2019/3/13/Rails-4-2-5-1-5-1-6-2-have-been-released/
• https://www.exploit-db.com/exploits/46785/
• http://packetstormsecurity.com/files/152704/Ruby-On-Rails-DoubleTap-Development-Mode-secret_key_base-Remote-Code-Execution.html
• https://groups.google.com/forum/#%21topic/rubyonrails-security/IsQKvDqZdKw
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Y43636TH4D6T46IC6N2RQVJTRFJAAYGA/
• https://weblog.rubyonrails.org/2019/3/13/Rails-4-2-5-1-5-1-6-2-have-been-released/
• https://www.exploit-db.com/exploits/46785/

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