CVE-2011-4293 in Moodle
Summary
by MITRE
The theme implementation in Moodle 2.0.x before 2.0.4 and 2.1.x before 2.1.1 triggers duplicate caching of Cascading Style Sheets (CSS) and JavaScript content, which allows remote attackers to bypass intended access restrictions and write to an operating-system temporary directory via unspecified vectors.
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Analysis
by VulDB Data Team • 12/06/2021
The vulnerability described in CVE-2011-4293 represents a critical security flaw in the Moodle learning management system that affects versions prior to 2.0.4 and 2.1.1. This issue stems from improper handling of CSS and JavaScript file caching mechanisms within Moodle's theme implementation, creating a scenario where duplicate caching operations can be exploited by remote attackers to gain unauthorized access to system resources. The vulnerability specifically targets the temporary directory management functionality of the operating system, allowing attackers to write malicious content to locations where they would normally not have permission to access. The flaw exists in the way Moodle processes and caches static content files, particularly when multiple requests attempt to cache the same resources simultaneously, leading to potential privilege escalation and unauthorized file system modifications.
The technical exploitation of this vulnerability involves leveraging the duplicate caching behavior to manipulate temporary file creation processes within the Moodle application. When the theme system attempts to cache CSS and JavaScript files, the improper implementation causes the system to create temporary files in locations accessible to the web server process. Attackers can manipulate the caching process to force the creation of files in system temporary directories, potentially leading to arbitrary code execution or privilege escalation. This issue is particularly dangerous because it combines multiple security weaknesses including improper access controls, temporary file handling vulnerabilities, and potential privilege escalation mechanisms. The vulnerability operates at the application layer and can be exploited remotely without requiring authentication, making it highly dangerous for web applications that are publicly accessible. The flaw demonstrates poor input validation and inadequate resource management practices that violate fundamental security principles.
The operational impact of this vulnerability extends beyond simple access restrictions, potentially allowing attackers to compromise entire Moodle installations and access sensitive educational data. Remote attackers can leverage this vulnerability to write malicious files to system temporary directories, which could then be executed by the web server or exploited for further attacks within the network. The consequences include potential data breaches, unauthorized access to student and faculty information, and possible complete system compromise. Organizations running affected Moodle versions face significant risk of unauthorized access to educational content and user data, as the vulnerability can be exploited by anyone with access to the web application. The impact is particularly severe in educational environments where Moodle systems often contain sensitive personal information, academic records, and confidential communication data. This vulnerability also demonstrates the importance of proper temporary file handling and access control mechanisms in web applications.
Mitigation strategies for CVE-2011-4293 require immediate patching of affected Moodle installations to versions 2.0.4 or 2.1.1, which contain the necessary fixes for the caching implementation. Organizations should also implement proper temporary directory access controls and ensure that web server processes have minimal necessary permissions to system resources. Security hardening measures include restricting write access to temporary directories, implementing proper input validation for file operations, and monitoring for unusual file creation patterns. Network segmentation and firewall rules should be configured to limit access to Moodle installations, while regular security audits should verify that temporary file handling follows secure coding practices. The vulnerability aligns with CWE-352 (Cross-Site Request Forgery) and CWE-73 (External Control of File Name or Path) categories, and maps to ATT&CK techniques including T1059 (Command and Scripting Interpreter) and T1078 (Valid Accounts) for potential exploitation paths. System administrators should also consider implementing intrusion detection systems to monitor for exploitation attempts and ensure that all Moodle components are regularly updated to prevent similar vulnerabilities from being exploited in the future.