CVE-2016-2154 in Moodle
Summary
by MITRE
admin/tool/monitor/lib.php in Event Monitor in Moodle 2.8.x before 2.8.11, 2.9.x before 2.9.5, and 3.0.x before 3.0.3 does not consider the moodle/course:viewhiddencourses capability, which allows remote authenticated users to discover hidden course names by subscribing to a rule.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/21/2022
The vulnerability identified as CVE-2016-2154 affects Moodle's Event Monitor component and represents a significant information disclosure flaw that undermines the platform's access control mechanisms. This issue exists within the admin/tool/monitor/lib.php file where the Event Monitor functionality fails to properly validate user permissions when processing course subscription requests. The flaw specifically impacts Moodle versions 2.8.x prior to 2.8.11, 2.9.x prior to 2.9.5, and 3.0.x prior to 3.0.3, creating a persistent security gap that affects organizations relying on Moodle's course hiding features for privacy and access control. The vulnerability stems from the Event Monitor's improper consideration of the moodle/course:viewhiddencourses capability, which is a fundamental permission control mechanism designed to restrict access to hidden courses within the learning management system.
The technical exploitation of this vulnerability occurs through a straightforward but effective attack vector that leverages the Event Monitor's subscription functionality. Remote authenticated users can manipulate the system by attempting to subscribe to monitoring rules for courses that should remain hidden from unauthorized access. The flaw operates because the system does not validate whether the requesting user possesses the necessary capability to view hidden courses before processing the subscription request. This allows attackers to bypass normal access controls and discover the names of courses that administrators have intentionally hidden from certain users or roles. The vulnerability essentially creates a reconnaissance mechanism that enables malicious actors to map the hidden course structure of a Moodle installation, potentially exposing sensitive educational content or administrative information.
From an operational impact perspective, this vulnerability significantly weakens the security posture of Moodle deployments by undermining the principle of least privilege and proper access control. Organizations that rely on hidden courses to maintain privacy for sensitive content, restricted access programs, or administrative functions face increased risk of information exposure. The vulnerability can be particularly damaging in educational environments where hidden courses might contain confidential student data, restricted access materials, or administrative functions that should remain private. The impact extends beyond simple information disclosure as it enables attackers to build detailed maps of course structures, potentially leading to more sophisticated attacks or unauthorized access to additional system components. Security administrators lose confidence in the platform's ability to maintain course privacy and access control, which can have broader implications for institutional data protection policies.
The vulnerability aligns with CWE-200, which addresses "Information Exposure," and demonstrates how improper access control validation can lead to unauthorized information disclosure. From an ATT&CK framework perspective, this issue maps to T1083 (File and Directory Discovery) and T1566 (Phishing), as attackers can use the information gained to craft more targeted attacks or to understand the target environment better. The flaw represents a classic case of insufficient input validation combined with inadequate privilege checking, where the system assumes that legitimate users will not attempt to access resources they should not be able to see. Organizations should implement immediate mitigations including upgrading to patched versions of Moodle, reviewing existing course access controls, and implementing additional monitoring for unusual subscription patterns. The recommended remediation involves ensuring that all access control checks properly validate the moodle/course:viewhiddencourses capability before allowing course subscription requests to proceed, thereby restoring the intended security boundaries within the platform.