CVE-2025-3647: Moodle Auth Bypass Vulnerability

CVE-2025-3647 Overview

A flaw was discovered in Moodle where additional checks were required to ensure that users can only access cohort data they are authorized to retrieve. This authorization bypass vulnerability allows authenticated users to potentially access cohort information beyond their intended permissions, exposing sensitive organizational data within the learning management system.

Critical Impact

Authenticated users may access unauthorized cohort data, potentially exposing student groupings, course enrollments, and organizational structures within Moodle installations.

Affected Products

• Moodle LMS (multiple versions affected)
• Moodle installations with cohort functionality enabled
• Organizations using Moodle cohorts for user management and course enrollment

Discovery Timeline

• 2025-04-25 - CVE-2025-3647 published to NVD
• 2025-06-24 - Last updated in NVD database

Technical Details for CVE-2025-3647

Vulnerability Analysis

This vulnerability is classified as CWE-863: Incorrect Authorization, which occurs when a product performs an authorization check incorrectly, allowing unauthorized actors to access resources or perform actions outside their intended privilege level.

In the context of Moodle, cohorts are site-wide or category-wide collections of users that enable bulk enrollment and management. The flaw exists in the authorization logic that should restrict cohort data access based on user permissions. When authenticated users make requests for cohort information, the system fails to properly validate whether the requesting user has the appropriate capabilities to view that specific cohort's data.

The vulnerability is exploitable over the network and requires low-privilege authentication to execute. While the impact is limited to information disclosure (confidentiality impact), unauthorized access to cohort data could reveal organizational structures, user groupings, and enrollment patterns that administrators intended to keep restricted.

Root Cause

The root cause stems from insufficient authorization checks in Moodle's cohort data retrieval functionality. The application fails to adequately verify user permissions before returning cohort information, allowing authenticated users to bypass intended access controls and retrieve data from cohorts they should not have visibility into.

Attack Vector

An authenticated attacker can exploit this vulnerability by making direct requests for cohort data through Moodle's web interface or API endpoints. Since the authorization checks are incomplete, the system may return cohort information for groups the attacker is not authorized to view. The attack requires valid authentication credentials but no special privileges beyond basic Moodle access.

The exploitation path involves:

1. Authenticating to a vulnerable Moodle instance with a standard user account
2. Crafting requests to access cohort data endpoints
3. Bypassing the insufficient authorization checks to retrieve unauthorized cohort information
4. Gaining access to user groupings, enrollment data, and organizational structures

Detection Methods for CVE-2025-3647

Indicators of Compromise

• Unusual patterns of cohort data access by non-administrative users
• Increased API calls to cohort-related endpoints from low-privilege accounts
• Access logs showing users querying cohorts outside their normal scope
• Anomalous data export activities involving cohort information

Detection Strategies

• Monitor Moodle access logs for unexpected cohort data retrieval patterns
• Implement alerting for cohort API endpoint access by non-administrative roles
• Review user activity reports for access to cohorts outside assigned categories
• Enable verbose logging on cohort-related functionality to track access attempts

Monitoring Recommendations

• Configure SIEM rules to detect bulk cohort data access from single user sessions
• Establish baseline patterns for normal cohort access and alert on deviations
• Regularly audit user permissions and cohort visibility settings
• Deploy web application monitoring to track cohort endpoint utilization

How to Mitigate CVE-2025-3647

Immediate Actions Required

• Update Moodle to the latest patched version immediately
• Review cohort visibility settings and restrict access to authorized users only
• Audit user roles and capabilities related to cohort management
• Enable additional logging to monitor for potential exploitation attempts

Patch Information

Moodle has released security updates to address this authorization bypass vulnerability. Administrators should consult the Moodle Forum Discussion Post for specific version information and upgrade guidance. Additional technical details are available in the Red Hat CVE-2025-3647 Advisory and Red Hat Bug Report #2359762.

Workarounds

• Restrict cohort management capabilities to trusted administrative users only
• Review and minimize the number of users with any cohort-related permissions
• Implement network-level access controls to limit access to administrative functions
• Consider disabling cohort functionality if not actively required until patching is complete
• Enable Moodle's additional security measures for API access control