CVE-2024-1439: Moodle LMS Privilege Escalation Flaw

CVE-2024-1439 Overview

CVE-2024-1439 is an inadequate access control vulnerability in Moodle LMS that allows unauthorized calendar event manipulation. This vulnerability could allow a local user with a student role to create arbitrary events intended for users with higher roles. It could also allow the attacker to add events to the calendar of all users without their prior consent.

Critical Impact

Users with low-privileged student accounts can bypass authorization controls to create and inject calendar events for higher-privileged users, potentially enabling social engineering attacks or disruption of academic workflows.

Affected Products

• Moodle LMS (all versions prior to patch)

Discovery Timeline

• 2024-02-12 - CVE-2024-1439 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-1439

Vulnerability Analysis

This vulnerability stems from broken access control within the Moodle LMS calendar functionality. The platform fails to properly validate user permissions when processing calendar event creation requests. Specifically, the authorization checks do not adequately verify that the requesting user has sufficient privileges to create events targeting other users or specific user roles.

In a properly secured implementation, calendar event creation should enforce role-based access control (RBAC) to ensure that users can only create events within their permission scope. However, this vulnerability allows users with student-level privileges to bypass these restrictions and create events that should only be accessible to administrators, teachers, or other elevated roles.

Root Cause

The root cause is classified under CWE-284 (Improper Access Control). The Moodle calendar module does not implement adequate permission verification during the event creation process. The system accepts event creation requests from authenticated users without properly validating whether the user's role authorizes them to target specific users or create events visible to higher-privileged accounts.

Attack Vector

The attack requires local access with an authenticated student account. An attacker exploiting this vulnerability would:

1. Authenticate to the Moodle LMS platform with a valid student account
2. Access the calendar event creation functionality
3. Craft event creation requests that target users with elevated privileges (teachers, administrators)
4. Successfully inject calendar events that appear in the calendars of targeted users

The exploitation does not require user interaction from the victim and can be performed without the knowledge or consent of affected users. This could be leveraged for social engineering campaigns, phishing-style attacks using trusted calendar notifications, or general disruption of the educational environment.

Detection Methods for CVE-2024-1439

Indicators of Compromise

• Unusual calendar event creation patterns from student accounts targeting administrative or teacher roles
• Calendar events appearing for users that were not created by appropriate privileged accounts
• Anomalous API requests to the calendar event creation endpoints from low-privileged sessions
• User reports of unexpected calendar events they did not create

Detection Strategies

• Monitor Moodle logs for calendar event creation activities, filtering for events created by student-role users that target other user accounts
• Implement alerting on bulk calendar event creation from single user sessions
• Review access logs for suspicious patterns in the calendar module API endpoints
• Deploy application-level logging to track authorization failures and privilege escalation attempts

Monitoring Recommendations

• Enable verbose logging for the Moodle calendar module to capture all event creation activities
• Establish baseline metrics for normal calendar usage patterns to identify anomalies
• Configure SIEM rules to correlate calendar event creation with user role information
• Implement periodic audits of calendar events to identify unauthorized entries

How to Mitigate CVE-2024-1439

Immediate Actions Required

• Review the INCIBE Notice on Moodle Vulnerability for specific remediation guidance
• Update Moodle LMS to the latest patched version as soon as available from the vendor
• Audit existing calendar events for unauthorized entries created by low-privileged users
• Consider temporarily restricting calendar event creation capabilities for student accounts until patched

Patch Information

Administrators should monitor official Moodle security announcements and apply the relevant security update addressing CVE-2024-1439. Review the INCIBE security notice for detailed patch information and remediation steps.

Workarounds

• Implement additional access control restrictions at the web application firewall level to limit calendar API access
• Configure Moodle role permissions to restrict calendar event creation for student accounts where feasible
• Enable enhanced logging and monitoring to detect exploitation attempts while awaiting a permanent patch
• Consider network segmentation to limit the exposure of the Moodle LMS to trusted networks only