CVE-2013-6415 in Ruby on Rails
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the number_to_currency helper in actionpack/lib/action_view/helpers/number_helper.rb in Ruby on Rails before 3.2.16 and 4.x before 4.0.2 allows remote attackers to inject arbitrary web script or HTML via the unit parameter.
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Analysis
by VulDB Data Team • 06/02/2021
The CVE-2013-6415 vulnerability represents a critical cross-site scripting flaw within the Ruby on Rails web framework that specifically targets the number_to_currency helper function. This vulnerability exists in actionpack/lib/action_view/helpers/number_helper.rb and affects versions prior to 3.2.16 and 4.x prior to 4.0.2, making it a widespread issue across multiple Rails release lines. The flaw stems from insufficient input validation and sanitization of the unit parameter within the currency formatting helper, which allows malicious actors to inject arbitrary JavaScript code or HTML content directly into web applications built on this framework.
The technical implementation of this vulnerability occurs when the number_to_currency helper processes user-supplied input through the unit parameter without proper sanitization. When a web application renders currency values using this helper function and passes unsanitized user data as the unit parameter, the framework fails to escape special characters that could be interpreted as HTML or JavaScript markup. This creates an exploitable condition where attackers can craft malicious payloads that execute in the context of other users' browsers when the vulnerable application renders currency information. The vulnerability falls under CWE-79, which specifically addresses Cross-Site Scripting flaws, and aligns with ATT&CK technique T1531 for "Modify Existing Service" and T1566 for "Phishing with Social Engineering" as attackers can leverage this to deliver malicious payloads through web interfaces.
The operational impact of CVE-2013-6415 extends beyond simple data theft, as it enables attackers to perform session hijacking, deface web applications, redirect users to malicious sites, or execute arbitrary commands within the context of user sessions. Applications using Rails frameworks that incorporate user-provided currency unit data are particularly vulnerable, including e-commerce platforms, financial applications, and any system that displays monetary values with customizable currency symbols. The vulnerability is especially dangerous because it can be exploited through various vectors including web forms, URL parameters, or API endpoints that accept currency unit specifications, making it difficult to fully mitigate without comprehensive input validation.
Mitigation strategies for CVE-2013-6415 require immediate patching of affected Rails versions to the recommended secure releases, specifically upgrading to Rails 3.2.16 or 4.0.2 and later. Organizations should also implement comprehensive input sanitization measures, including HTML escaping of all user-provided parameters before processing, and establish strict validation protocols for currency unit inputs. Additional defensive measures include implementing Content Security Policy headers to limit script execution, using web application firewalls to detect and block suspicious input patterns, and conducting regular security audits of all helper functions that process user data. The vulnerability demonstrates the critical importance of proper input validation in web applications and reinforces the necessity of following security best practices such as those outlined in OWASP Top Ten and NIST SP 800-53 security controls.