CVE-2015-5266 in Moodle
Summary
by MITRE
The enrol_meta_sync function in enrol/meta/locallib.php in Moodle through 2.6.11, 2.7.x before 2.7.10, 2.8.x before 2.8.8, and 2.9.x before 2.9.2 allows remote authenticated users to obtain manager privileges in opportunistic circumstances by leveraging incorrect role processing during a long-running sync script.
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Analysis
by VulDB Data Team • 07/08/2022
The vulnerability identified as CVE-2015-5266 resides within the Moodle learning management system's enrolment synchronization mechanism, specifically in the enrol_meta_sync function located in enrol/meta/locallib.php. This flaw affects multiple versions of Moodle including 2.6.11 and earlier, 2.7.x versions before 2.7.10, 2.8.x versions before 2.8.8, and 2.9.x versions before 2.9.2. The security issue represents a critical privilege escalation vulnerability that allows authenticated remote attackers to gain manager privileges under specific conditions. The vulnerability stems from improper role handling during long-running synchronization processes, creating a window of opportunity for attackers to exploit the system's access control mechanisms.
The technical flaw manifests in the incorrect processing of user roles during the meta enrolment synchronization script execution. When Moodle performs enrolment synchronization, particularly in environments where multiple courses are interconnected through meta enrolment, the system fails to properly validate and process role assignments. This occurs during extended sync operations where the system's role management logic becomes inconsistent, allowing attackers who have already authenticated to the system to manipulate their privileges. The vulnerability specifically targets the role assignment logic that should prevent unauthorized privilege elevation, but due to the flawed implementation in the sync function, it creates opportunities for privilege escalation under certain circumstances.
The operational impact of this vulnerability is significant for organizations relying on Moodle for educational management. Remote authenticated users who can access the system can potentially escalate their privileges from regular user or teacher roles to manager level access, which typically includes full administrative capabilities within course contexts. This allows attackers to modify course content, manage user accounts, configure system settings, and potentially access sensitive data that should be restricted to authorized administrators only. The opportunistic nature of the vulnerability means that exploitation is not guaranteed in every scenario but becomes possible when specific conditions align during the long-running sync processes, making it particularly dangerous in environments where such synchronization operations occur frequently.
Organizations should implement immediate mitigations including updating to the patched versions of Moodle that address this vulnerability, specifically versions 2.6.12, 2.7.10, 2.8.8, and 2.9.2 respectively. The fix involves correcting the role processing logic within the enrol_meta_sync function to ensure proper validation and assignment of user roles during synchronization operations. System administrators should also consider implementing additional monitoring and access controls to detect unusual privilege changes and limit the scope of users who can initiate enrolment synchronization processes. This vulnerability aligns with CWE-284 Access Control Issues and can be mapped to ATT&CK technique T1078 Valid Accounts, as it leverages legitimate authenticated user sessions to escalate privileges. The remediation strategy should include regular security updates, comprehensive access control reviews, and continuous monitoring of user privilege changes to prevent unauthorized escalation of access rights within the Moodle environment.