CVE-2016-8643 in Moodle
Summary
by MITRE
In Moodle 2.x and 3.x, non-admin site managers may accidentally edit admins via web services.
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2016-8643 represents a critical access control flaw within the Moodle learning management system affecting versions 2.x and 3.x. This issue stems from insufficient authorization checks within the web services framework, specifically in how the system handles user management operations through its Application Programming Interface. The flaw allows users with site manager privileges but without administrative rights to inadvertently modify administrator accounts through the web services interface, creating a significant security risk that undermines the principle of least privilege.
This vulnerability operates through the web services layer of Moodle where the system fails to properly validate whether the requesting user has sufficient privileges to modify accounts with higher permission levels. The technical implementation flaw lies in the absence of proper access control enforcement when processing user management requests through the web services API. When a site manager attempts to edit a user account via web services, the system does not adequately verify that the target user's permission level is within the requesting user's authorized scope, allowing privilege escalation through indirect means.
The operational impact of this vulnerability extends beyond simple unauthorized access as it enables non-administrative users to potentially compromise system integrity and user data. Attackers could exploit this flaw to modify administrator accounts, change passwords, alter permissions, or even delete administrative accounts entirely, leading to complete system compromise. The vulnerability is particularly dangerous because it operates through legitimate web services interfaces that are often enabled in production environments, making detection difficult and exploitation relatively straightforward. This flaw directly violates security principles outlined in the CWE catalog under category 285, which addresses improper authorization issues in software systems.
Mitigation strategies for CVE-2016-8643 require immediate implementation of enhanced access control measures within the web services framework. Organizations should ensure that web services interfaces properly enforce authorization checks by implementing strict validation of user privileges before allowing any modification operations. The recommended approach includes configuring web service access controls to prevent site managers from accessing administrative accounts, implementing role-based access controls that explicitly restrict account modification permissions, and ensuring that all web service operations validate both the requesting user's permissions and the target account's privilege level. Additionally, administrators should disable unnecessary web services, regularly audit web service usage, and implement monitoring systems to detect unauthorized account modification attempts. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the T1078 credential access sub-technique where attackers leverage system weaknesses to gain elevated privileges through legitimate system interfaces.