CVE-2024-43425: Moodle RCE Vulnerability

CVE-2024-43425 Overview

A remote code execution vulnerability has been identified in Moodle's calculated question types functionality. The flaw stems from insufficient restrictions in the question handling mechanism, which could allow attackers to execute arbitrary code on affected Moodle installations. Exploitation of this vulnerability requires the capability to add or update questions within the learning management system.

Critical Impact

Remote code execution in Moodle calculated question types allows attackers with question management privileges to compromise the learning management system and potentially gain control of the underlying server.

Affected Products

• Moodle LMS (multiple versions affected)
• Moodle calculated question type module

Discovery Timeline

• 2024-11-07 - CVE-2024-43425 published to NVD
• 2025-05-01 - Last updated in NVD database

Technical Details for CVE-2024-43425

Vulnerability Analysis

This vulnerability is classified as CWE-94 (Improper Control of Generation of Code, also known as Code Injection). The flaw exists within Moodle's calculated question types feature, which allows educators to create mathematical questions with dynamically generated values. The vulnerability allows remote code execution when an attacker with question creation or modification privileges crafts a malicious calculated question.

The attack requires network access and exploits insufficient input validation in the question processing logic. While the attack complexity is considered high due to the prerequisite access requirements, successful exploitation can lead to complete system compromise with impacts to confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause of this vulnerability lies in inadequate restrictions and input sanitization within the calculated question type processing engine. Moodle's calculated questions support mathematical formulas that are evaluated server-side, and the vulnerability exists because the formula evaluation mechanism does not properly restrict or sanitize inputs that could lead to code execution.

Attack Vector

The attack vector is network-based, requiring an authenticated user with permissions to add or update questions in Moodle. An attacker would need to:

1. Authenticate to a vulnerable Moodle instance
2. Navigate to the question management functionality
3. Create or modify a calculated question type
4. Inject malicious code through the formula or variable fields
5. Trigger the evaluation of the malicious calculated question

The vulnerability allows attackers to break out of the intended mathematical evaluation context and execute arbitrary code on the server. This could lead to data theft, system compromise, or use of the server for further attacks.

Detection Methods for CVE-2024-43425

Indicators of Compromise

• Unusual or suspicious calculated questions containing non-mathematical syntax or shell commands
• Unexpected process execution originating from the Moodle web application
• Anomalous network connections from the Moodle server to external hosts
• Web application logs showing unusual POST requests to question creation/editing endpoints

Detection Strategies

• Monitor Moodle question database tables for calculated questions containing suspicious patterns or escape sequences
• Implement web application firewall (WAF) rules to detect code injection patterns in question creation requests
• Review audit logs for unauthorized question creation or modification activities
• Deploy endpoint detection and response (EDR) solutions to detect suspicious process spawning from web server processes

Monitoring Recommendations

• Enable comprehensive logging for Moodle question management activities
• Configure alerts for new calculated question creation by non-trusted users
• Monitor server resource utilization for anomalies that might indicate exploitation
• Implement file integrity monitoring on Moodle installation directories

How to Mitigate CVE-2024-43425

Immediate Actions Required

• Review and restrict user permissions for question creation and modification capabilities
• Audit existing calculated questions for potentially malicious content
• Apply available security patches from Moodle immediately
• Consider temporarily disabling calculated question types until patching is complete

Patch Information

Moodle has released security updates to address this vulnerability. Organizations should apply the latest security patches as soon as possible. Detailed information about the security fix is available in the Moodle Forum Discussion #461193. Additional technical details can be found in Red Hat Bug Report #2304253.

Workarounds

• Restrict the moodle/question:add and moodle/question:editall capabilities to trusted users only
• Implement network segmentation to limit the impact of potential exploitation
• Deploy a web application firewall with rules to detect and block code injection attempts
• Consider disabling calculated question types if not required for your educational environment

# Example: Restrict question capabilities in Moodle (review and adjust for your environment)
# Access Site administration > Users > Permissions > Define roles
# Review and restrict the following capabilities for non-trusted roles:
# - moodle/question:add
# - moodle/question:editall
# - moodle/question:editmine
# Ensure only trusted educators have question management permissions