CVE-2006-0461 in ExpressionEngine
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in core.input.php in ExpressionEngine 1.4.1 allows remote attackers to inject arbitrary web script or HTML via HTTP_REFERER (referer).
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Analysis
by VulDB Data Team • 07/18/2018
The vulnerability identified as CVE-2006-0461 represents a classic cross-site scripting flaw within ExpressionEngine version 1.4.1, specifically affecting the core.input.php component. This security weakness arises from insufficient input validation and sanitization of the HTTP_REFERER header, which is commonly used by web applications to track user navigation paths. The vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is one of the most prevalent and well-documented web application security flaws in the industry.
The technical exploitation of this vulnerability occurs when a remote attacker manipulates the HTTP_REFERER header to include malicious script code or HTML content. When ExpressionEngine processes this unvalidated input within its core.input.php file, the application fails to properly escape or sanitize the referer data before rendering it in web pages. This allows attackers to inject arbitrary web scripts that execute in the context of other users' browsers who visit pages that process this malicious referer information. The attack vector is particularly insidious because HTTP_REFERER headers are often automatically populated by web browsers and are not typically subject to strict user input validation.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it enables attackers to perform session hijacking, steal sensitive cookies, redirect users to malicious websites, or execute persistent malicious scripts that can compromise user sessions. Given that ExpressionEngine was a popular content management system in the mid-2000s, this vulnerability could have affected numerous websites and web applications that relied on the platform for content management. The vulnerability's persistence stems from the fact that the referer header is often passed through multiple layers of application processing without adequate sanitization, creating multiple potential injection points.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and output encoding mechanisms. The primary defense involves sanitizing all user-supplied input, including HTTP_REFERER headers, by implementing proper HTML escaping before any data is rendered in web pages. This approach aligns with the defensive programming principles outlined in the OWASP Top Ten and follows the ATT&CK framework's mitigation techniques for web application vulnerabilities. Organizations should also consider implementing Content Security Policy headers to prevent unauthorized script execution, while regular security audits and input validation testing should be integrated into development lifecycle processes to prevent similar issues in future versions. The vulnerability serves as a historical example of why proper input validation and output encoding are fundamental security requirements in web application development, particularly in content management systems that process user-generated content or metadata from HTTP headers.