CVE-2024-33999
📋 TL;DR
This vulnerability in Moodle's MFA system allows attackers to bypass multi-factor authentication by manipulating the referrer URL. It affects Moodle installations with MFA enabled, potentially compromising user accounts and administrative access.
💻 Affected Systems
- Moodle
📦 What is this software?
Moodle by Moodle
⚠️ Risk & Real-World Impact
Worst Case
Complete account takeover including administrative accounts, leading to data theft, system compromise, and unauthorized access to sensitive information.
Likely Case
Unauthorized access to user accounts, potential privilege escalation, and compromise of personal or institutional data.
If Mitigated
Limited impact with proper network segmentation and monitoring, but still represents an authentication bypass vulnerability.
🎯 Exploit Status
Exploitation requires understanding of the MFA flow and ability to manipulate HTTP referrer headers. No public exploit code identified in provided references.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in provided references, but Moodle security updates typically address such vulnerabilities.
Vendor Advisory: https://moodle.org/mod/forum/discuss.php?d=458387
Restart Required: No
Instructions:
1. Update Moodle to the latest security release. 2. Apply the patch that adds proper sanitization to referrer URL handling in MFA. 3. Verify MFA functionality post-update.
🔧 Temporary Workarounds
Disable MFA temporarily
allTemporarily disable multi-factor authentication until patch can be applied.
Navigate to Site administration > Plugins > Authentication > Manage authentication > Disable MFA methods
Web Application Firewall rule
allAdd WAF rule to sanitize or block suspicious referrer URLs in MFA requests.
Configure WAF to inspect and sanitize Referer headers in /login/* paths
🧯 If You Can't Patch
- Implement network-level controls to restrict access to Moodle administration interfaces
- Enable enhanced logging and monitoring for MFA bypass attempts and unusual authentication patterns
🔍 How to Verify
Check if Vulnerable:
Check Moodle version and review MFA configuration. Test if referrer manipulation during MFA flow allows authentication bypass.Check Version:
Check Moodle version via Site administration > Notifications page or by examining version.php fileVerify Fix Applied:
Verify Moodle is updated to patched version and test MFA functionality with various referrer scenarios.📡 Detection & Monitoring
Log Indicators:
- Unusual referrer URLs in authentication logs
- MFA bypass attempts
- Multiple failed MFA attempts followed by successful login
Network Indicators:
- HTTP requests with manipulated Referer headers to MFA endpoints
- Unusual authentication patterns
SIEM Query:
source="moodle_logs" AND (event="authentication" OR event="mfa") AND (referrer CONTAINS suspicious_pattern OR referrer IS NULL)