CVE-2012-6684 in RedCloth Library
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the RedCloth library 4.2.9 for Ruby and earlier allows remote attackers to inject arbitrary web script or HTML via a javascript: URI.
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Analysis
by VulDB Data Team • 04/27/2025
The CVE-2012-6684 vulnerability represents a critical cross-site scripting flaw within the RedCloth library version 4.2.9 and earlier releases for the Ruby programming language. This vulnerability exposes applications that utilize RedCloth for text processing to potential malicious code injection attacks, where remote adversaries can execute arbitrary web scripts or HTML content through specially crafted input. The RedCloth library serves as a text processing tool that converts plain text into HTML format, making it a common component in web applications that handle user-generated content. The vulnerability specifically manifests when the library fails to properly sanitize input containing javascript: URIs, which are commonly used to execute client-side scripts in web browsers. This flaw allows attackers to bypass normal input validation mechanisms and inject malicious payloads directly into the HTML output generated by the library.
The technical exploitation of this vulnerability occurs when user input containing a javascript: URI is processed by RedCloth without adequate sanitization. When the library encounters such input, it fails to properly escape or filter the URI scheme, allowing the malicious script to be embedded directly into the generated HTML document. This creates an environment where any web page utilizing RedCloth for text processing becomes susceptible to XSS attacks, as the malicious script will execute in the context of any user who views the affected content. The vulnerability stems from insufficient input validation and output encoding practices within the RedCloth processing pipeline, which should have implemented proper sanitization measures to prevent such dangerous URI schemes from being rendered as executable code. This type of vulnerability is classified under CWE-79 as Improper Neutralization of Input During Web Page Generation, specifically manifesting as a cross-site scripting issue. The flaw demonstrates poor secure coding practices that violate fundamental web security principles.
The operational impact of CVE-2012-6684 extends beyond simple script injection, as it can enable attackers to perform a wide range of malicious activities including session hijacking, credential theft, and data exfiltration. When exploited, this vulnerability allows attackers to execute scripts in the victim's browser context, potentially leading to full account compromise if users are authenticated. The vulnerability affects web applications across various domains that rely on RedCloth for content processing, including content management systems, blog platforms, and any application that accepts user input and renders it as HTML. Attackers can craft malicious input that appears legitimate but contains embedded javascript: URIs, which when processed by the vulnerable RedCloth library will execute in the browser of any user viewing the affected content. The impact is particularly severe in environments where users have administrative privileges or where sensitive data is processed through these vulnerable applications, as the malicious scripts could potentially access and exfiltrate confidential information.
Mitigation strategies for CVE-2012-6684 require immediate action to upgrade to RedCloth version 4.3.0 or later, which contains the necessary patches to address the XSS vulnerability. Organizations should implement comprehensive input validation and output encoding mechanisms to prevent similar vulnerabilities from occurring in other components of their web applications. The remediation process involves not only updating the vulnerable library but also conducting thorough security assessments of all applications that utilize RedCloth or similar text processing libraries. Security teams should implement proper content security policies and sanitize all user input before processing, ensuring that javascript: URIs and other dangerous patterns are properly filtered or escaped. Additionally, organizations should consider implementing web application firewalls and runtime protection mechanisms to detect and prevent exploitation attempts. This vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript, demonstrating how insecure input handling can enable execution of malicious scripts in web environments. The remediation process should also include comprehensive testing to ensure that the updated library functions correctly and that no regressions have been introduced in the application's text processing capabilities.