CVE-2008-1133 in Drupal
Summary
by MITRE
The Drupal.checkPlain function in Drupal 6.0 only escapes the first instance of a character in ECMAScript, which allows remote attackers to conduct cross-site scripting (XSS) attacks.
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Analysis
by VulDB Data Team • 09/19/2018
The vulnerability identified as CVE-2008-1133 represents a critical cross-site scripting flaw in the Drupal content management system version 6.0. This issue stems from a fundamental flaw in the Drupal.checkPlain function implementation that fails to properly escape all instances of special characters within user-supplied input. The vulnerability specifically affects how the function handles character escaping in ECMAScript contexts, creating a pathway for malicious actors to inject persistent XSS payloads. The flaw demonstrates a classic improper input validation weakness that has been categorized under CWE-79, which addresses cross-site scripting vulnerabilities in software applications.
The technical implementation of this vulnerability occurs within the Drupal.checkPlain function where developers intended to sanitize user input by escaping special characters to prevent malicious script execution. However, the function's design only processes and escapes the first occurrence of each potentially dangerous character rather than all instances throughout the input string. This incomplete sanitization allows attackers to craft input containing multiple instances of characters like quotes, angle brackets, or other script delimiters where only the initial character gets escaped while subsequent occurrences remain unfiltered. This behavior creates a persistent vulnerability that can be exploited across multiple contexts where user input is rendered without additional sanitization, particularly in areas where the function's output is subsequently processed or displayed.
The operational impact of this vulnerability extends beyond simple XSS exploitation to potentially enable more sophisticated attack vectors including session hijacking, credential theft, and unauthorized administrative access. Attackers can leverage this flaw to inject malicious scripts that execute in the context of other users' browsers, potentially compromising entire user sessions and gaining access to sensitive administrative functions. The vulnerability affects the core rendering pipeline of Drupal applications, making it particularly dangerous as it can be exploited across multiple modules and components that rely on the checkPlain function for input sanitization. This flaw aligns with ATT&CK technique T1059.007 for command and scripting interpreter usage and T1566 for credential access through social engineering, as the exploitation can lead to broader compromise of the web application environment.
Mitigation strategies for CVE-2008-1133 require immediate application of the official Drupal security patch that corrects the checkPlain function implementation to properly escape all instances of special characters rather than just the first occurrence. Organizations should implement comprehensive input validation at multiple layers including client-side and server-side sanitization, deploy web application firewalls to detect and block suspicious input patterns, and conduct thorough security testing of all user input handling functions. The fix should ensure that all instances of potentially dangerous characters are properly escaped according to established security standards and that the sanitization process operates consistently across all input processing contexts. Additionally, regular security audits and code reviews should be implemented to identify similar patterns of incomplete sanitization that could lead to similar vulnerabilities in other parts of the application stack.