CVE-2019-3852 in Moodle
Summary
by MITRE
A vulnerability was found in moodle before version 3.6.3. The get_with_capability_join and get_users_by_capability functions were not taking context freezing into account when checking user capabilities
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Analysis
by VulDB Data Team • 09/08/2025
The vulnerability identified as CVE-2019-3852 affects Moodle versions prior to 3.6.3 and represents a significant capability checking flaw that undermines the platform's access control mechanisms. This issue resides within the core user permission system where the get_with_capability_join and get_users_by_capability functions fail to properly account for context freezing during capability validation processes. The vulnerability stems from inadequate consideration of the context freezing mechanism that should prevent users from accessing capabilities beyond their intended scope within specific contexts.
The technical flaw manifests when Moodle processes user capability checks through these specific functions, which are designed to retrieve users who possess certain capabilities within defined contexts. When context freezing is enabled, it should prevent capability checks from traversing across context boundaries, but the affected functions bypass this critical security measure. This oversight allows authenticated users to potentially escalate their privileges and access capabilities they should not normally possess, effectively creating a path for unauthorized access to restricted resources and functionality. The flaw operates at the database query level where joins and user filtering occur, making it particularly dangerous as it can be exploited through various legitimate user interactions with the platform.
The operational impact of CVE-2019-3852 extends beyond simple privilege escalation, as it can enable attackers to gain access to sensitive data, manipulate user accounts, and potentially compromise entire Moodle instances. An attacker exploiting this vulnerability could access course materials, user information, and administrative functions that should be restricted to specific user roles. The vulnerability is particularly concerning in multi-tenant environments where different users share the same Moodle instance but should have distinct access levels. The flaw affects the fundamental security model of Moodle's capability system, which is designed to enforce role-based access control through context-aware capability checks.
Organizations using Moodle versions prior to 3.6.3 should prioritize immediate remediation through the official Moodle update process, as this vulnerability can be exploited without requiring elevated privileges or special tools. The fix implemented in version 3.6.3 properly addresses the context freezing consideration within the affected functions, ensuring that capability checks respect the boundaries established by context freezing mechanisms. Security teams should also conduct thorough audits of user roles and capabilities following the patch deployment to verify that no unauthorized access patterns have occurred. This vulnerability aligns with CWE-284, which addresses improper access control, and represents a specific implementation flaw in capability management that can be mapped to ATT&CK technique T1078 for valid accounts and privilege escalation.
The remediation process involves updating Moodle to version 3.6.3 or later, which includes the necessary code modifications to properly handle context freezing during capability checks. Administrators should also review their current capability assignments and context configurations to ensure that existing access controls remain effective post-patch. Additional security measures such as monitoring for unusual user activity patterns and implementing proper network segmentation can provide defense-in-depth protection. The vulnerability demonstrates the critical importance of context-aware security controls in learning management systems where user roles and permissions must be strictly enforced across different educational contexts and course environments.