CVE-2020-8167 in Ruby on Rails
Summary
by MITRE
A CSRF vulnerability exists in rails <= 6.0.3 rails-ujs module that could allow attackers to send CSRF tokens to wrong domains.
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Analysis
by VulDB Data Team • 06/21/2020
The vulnerability identified as CVE-2020-8167 represents a critical cross-site request forgery weakness within the rails-ujs module of ruby on rails framework versions 6.0.3 and earlier. This flaw specifically impacts the client-side javascript implementation responsible for handling csrf protection mechanisms in web applications built on the rails framework. The vulnerability arises from improper validation of the domain associated with csrf tokens, creating a scenario where malicious actors can exploit the token handling process to perform unauthorized actions against unintended targets.
The technical implementation flaw occurs within the rails-ujs javascript library where csrf tokens are validated and transmitted during ajax requests and form submissions. When applications utilize the rails-ujs functionality for csrf protection, the library fails to adequately verify that the csrf token originates from the same domain as the request being processed. This allows attackers to craft malicious requests that include valid csrf tokens from one domain while targeting resources on another domain, effectively bypassing the intended security controls designed to prevent csrf attacks.
The operational impact of this vulnerability extends beyond traditional csrf attack vectors, creating potential for more sophisticated exploitation patterns. An attacker could leverage this weakness to perform actions on behalf of authenticated users against different domains where the csrf token might be valid, particularly in environments where applications share csrf token validation mechanisms or where token reuse patterns exist. This opens possibilities for data exfiltration, unauthorized transactions, account takeovers, and other malicious activities that could compromise user data and application integrity.
Security professionals should implement immediate mitigations including upgrading to rails version 6.0.4 or later where this vulnerability has been addressed through proper domain validation of csrf tokens. Additionally, organizations should conduct comprehensive reviews of their csrf token handling implementations to ensure proper domain validation is enforced at both client and server levels. The vulnerability aligns with CWE-352, which specifically addresses cross-site request forgery weaknesses, and represents a direct violation of secure coding practices for maintaining proper request origin validation. From an ATT&CK framework perspective, this vulnerability maps to technique T1531, specifically targeting the exploitation of web application security controls through manipulation of request parameters and token validation mechanisms. Organizations should also consider implementing additional security layers such as content security policies and proper header validation to provide defense-in-depth against potential exploitation attempts.