CVE-2012-3388 in Moodle
Summary
by MITRE
The is_enrolled function in lib/accesslib.php in Moodle 2.2.x before 2.2.4 and 2.3.x before 2.3.1 does not properly interact with the caching feature, which might allow remote authenticated users to bypass an intended capability check via unspecified vectors that trigger caching of a user record.
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Analysis
by VulDB Data Team • 12/06/2021
The vulnerability identified as CVE-2012-3388 affects Moodle learning management systems version 2.2.x before 2.2.4 and 2.3.x before 2.3.1, specifically within the lib/accesslib.php file where the is_enrolled function operates. This flaw represents a critical access control bypass vulnerability that stems from improper handling of the system's caching mechanism. The issue occurs when the function fails to correctly manage cached user records, creating a scenario where authenticated users can exploit the system's caching behavior to circumvent intended capability checks. The vulnerability is particularly concerning because it allows remote authenticated users to gain unauthorized access to resources they should not be permitted to access, effectively undermining the platform's security model.
The technical root cause of this vulnerability lies in the interaction between the is_enrolled function and Moodle's caching infrastructure. When user records are cached and subsequently retrieved, the function does not properly validate or refresh the cached data to ensure that current enrollment status and capabilities remain accurate. This caching inconsistency creates a window where a user's cached enrollment information may not reflect their actual current status, particularly when enrollment status changes or when access permissions are modified. The unspecified vectors that trigger this behavior likely involve scenarios where user records are cached during one access operation and then subsequently retrieved without proper validation during a different access operation. This flaw falls under the CWE-200 category of "Information Exposure" and more specifically relates to CWE-284 "Improper Access Control" as it allows unauthorized access to protected resources through improper capability validation.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can potentially allow authenticated users to access course materials, administrative functions, or other restricted resources that should only be available to specific enrolled users or particular user roles. Attackers could exploit this vulnerability to gain access to sensitive course content, view grades, access restricted forums, or potentially perform administrative actions depending on the specific capabilities of the compromised user account. The remote nature of the attack means that an authenticated user can leverage this vulnerability from any location without requiring physical access to the system. This represents a significant threat to the integrity of Moodle's role-based access control system and could lead to data breaches, unauthorized content exposure, or disruption of educational services. The vulnerability affects the core access control mechanisms that are fundamental to maintaining the security and privacy of educational platforms.
Mitigation strategies for this vulnerability should focus on ensuring proper cache invalidation and validation of user enrollment status during capability checks. System administrators should immediately upgrade to Moodle versions 2.2.4 or 2.3.1, which contain the necessary patches to address the caching inconsistency in the is_enrolled function. Additionally, organizations should implement monitoring to detect unusual access patterns that might indicate exploitation attempts, particularly around enrollment status changes or access to restricted resources. The implementation of proper cache management practices, including ensuring that cached user records are invalidated when enrollment status changes, can help prevent similar issues. From an ATT&CK perspective, this vulnerability aligns with techniques involving privilege escalation and defense evasion, as attackers could use it to maintain persistent access to restricted resources while avoiding detection through normal access controls. Regular security audits of access control implementations and proper testing of caching mechanisms should be part of ongoing security maintenance to prevent similar vulnerabilities from emerging in the future.