CVE-2022-30600: Moodle Auth Bypass Vulnerability

CVE-2022-30600 Overview

A critical authentication bypass vulnerability was discovered in Moodle, the widely-used open-source learning management system (LMS). The flaw exists in the logic used to count failed login attempts, which could allow attackers to bypass the account lockout threshold. This vulnerability enables brute-force attacks against user accounts without triggering the standard security controls designed to prevent such attacks.

Critical Impact

Attackers can bypass account lockout protections to conduct unlimited brute-force attacks against Moodle user credentials, potentially compromising student, instructor, and administrator accounts.

Affected Products

• Moodle versions prior to patched releases (including version 4.0.0)
• Red Hat Enterprise Linux 8.0
• Fedora Linux 34, 35, and 36

Discovery Timeline

• May 18, 2022 - CVE-2022-30600 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-30600

Vulnerability Analysis

This vulnerability stems from a logical error in how Moodle tracks and counts failed login attempts. The account lockout mechanism is a critical security feature designed to prevent brute-force password attacks by temporarily locking accounts after a specified number of failed login attempts. However, due to flawed counting logic, the threshold counter could be manipulated or circumvented, rendering this protection ineffective.

The authentication bypass allows attackers to attempt password guessing attacks without ever triggering the lockout mechanism. In educational environments, this is particularly concerning as Moodle instances often contain sensitive academic data, student information, and administrative access credentials.

Root Cause

The root cause is classified as CWE-682: Incorrect Calculation. The login attempt counter contains a computational or logical error that prevents it from accurately tracking the number of failed authentication attempts. This miscalculation allows the lockout threshold to be bypassed, enabling unlimited login attempts against target accounts.

Attack Vector

The vulnerability is exploitable over the network without requiring any authentication or user interaction. An attacker can target any Moodle instance exposed to the network by:

1. Identifying valid usernames through enumeration or reconnaissance
2. Initiating automated login attempts against target accounts
3. Exploiting the counter bypass to avoid triggering account lockout
4. Continuing brute-force attacks until valid credentials are discovered

The attack requires no privileges or special access, making it accessible to any threat actor who can reach the Moodle login interface. The vulnerability mechanism involves manipulating login requests in a way that the failed attempt counter does not properly increment, allowing attackers to continue password guessing attempts indefinitely. For complete technical details, refer to the Moodle Forum Discussion and the Moodle Commit Reference.

Detection Methods for CVE-2022-30600

Indicators of Compromise

• High volume of failed login attempts from single IP addresses without corresponding account lockouts
• Unusual patterns in authentication logs showing repeated login failures for the same username
• Successful logins following extended periods of failed attempts that should have triggered lockout
• Authentication log anomalies where lockout events are absent despite numerous failures

Detection Strategies

• Implement external monitoring of authentication logs independent of Moodle's built-in mechanisms
• Deploy web application firewalls (WAF) with rate limiting on login endpoints
• Use SIEM solutions to correlate login attempt patterns and detect brute-force activity
• Monitor for login attempts that bypass expected lockout thresholds

Monitoring Recommendations

• Review Moodle authentication logs regularly for anomalous login patterns
• Set up alerting for high-frequency login failures that don't trigger lockouts
• Compare actual lockout events against expected behavior based on configuration
• Monitor network traffic to login endpoints for automated attack signatures

How to Mitigate CVE-2022-30600

Immediate Actions Required

• Upgrade Moodle to the latest patched version immediately
• Implement additional rate limiting at the network or application layer
• Review authentication logs for evidence of exploitation
• Consider enabling multi-factor authentication (MFA) for all accounts
• Temporarily restrict access to the login page to trusted IP ranges if possible

Patch Information

Moodle has released patches addressing this vulnerability. Organizations should update to the latest stable release. The fix is tracked under identifier MDL-73736 in the Moodle development tracker. Patches are available through the Moodle Git Repository. Users of Fedora can obtain updates through the official package repositories as documented in the Fedora Package Announcements. Red Hat users should refer to the Red Hat Bug Report for Enterprise Linux guidance.

Workarounds

• Deploy a reverse proxy with rate limiting in front of Moodle login pages
• Implement IP-based blocking for sources generating excessive login attempts
• Enable CAPTCHA on the login form to impede automated attacks
• Use network-level controls to restrict login page access to known IP ranges

# Example: Nginx rate limiting configuration for Moodle login endpoint
limit_req_zone $binary_remote_addr zone=login:10m rate=5r/m;

server {
    location /login/index.php {
        limit_req zone=login burst=3 nodelay;
        proxy_pass http://moodle_backend;
    }
}