CVE-2025-62399: Moodle Auth Bypass Vulnerability

CVE-2025-62399 Overview

CVE-2025-62399 is a high-severity authentication vulnerability affecting Moodle's mobile and web service authentication endpoints. The flaw stems from insufficient rate limiting on repeated password attempts, making the authentication mechanisms susceptible to brute-force attacks. This improper restriction of excessive authentication attempts (CWE-307) could allow attackers to systematically guess user credentials, potentially leading to unauthorized account access.

Critical Impact

Moodle learning management systems are exposed to credential brute-forcing through mobile and web service endpoints, potentially compromising student and administrator accounts across educational institutions.

Affected Products

• Moodle LMS (multiple versions affected)
• Moodle Mobile Web Services
• Moodle Web Service Authentication Endpoints

Discovery Timeline

• October 23, 2025 - CVE-2025-62399 published to NVD
• November 14, 2025 - Last updated in NVD database

Technical Details for CVE-2025-62399

Vulnerability Analysis

This vulnerability represents a classic improper restriction of excessive authentication attempts scenario. Moodle's mobile and web service authentication endpoints lack adequate controls to prevent automated password guessing attacks. When authentication services fail to implement proper rate limiting, account lockout mechanisms, or progressive delays after failed attempts, attackers can leverage automated tools to systematically test credential combinations.

The network-accessible nature of this vulnerability means remote attackers can conduct brute-force campaigns without any prior authentication or user interaction. The vulnerability's impact primarily manifests as a denial of service condition through resource exhaustion, though successful credential guessing could lead to unauthorized access to user accounts.

Educational institutions running vulnerable Moodle instances face significant risk, as learning management systems typically contain sensitive academic records, personal student information, and administrative functions.

Root Cause

The root cause is the absence of sufficient authentication attempt restrictions on Moodle's mobile and web service endpoints. The authentication handlers fail to implement necessary safeguards such as:

• Account lockout thresholds after consecutive failed attempts
• Progressive time delays between authentication requests
• CAPTCHA challenges after suspicious activity
• IP-based rate limiting for authentication requests

This allows attackers to submit unlimited authentication requests without triggering protective countermeasures.

Attack Vector

The attack vector is network-based, requiring no prior authentication or user interaction. An attacker can target Moodle's mobile API endpoints or web service authentication URLs with automated credential testing tools. The attacker would typically:

1. Enumerate valid usernames through reconnaissance or information disclosure
2. Configure automated brute-force tools targeting the vulnerable endpoints
3. Submit rapid authentication attempts using common password lists or targeted dictionaries
4. Monitor responses to identify successful authentication attempts

Due to the lack of rate limiting, attackers can achieve high request volumes, significantly increasing the probability of discovering valid credentials within a reasonable timeframe.

Detection Methods for CVE-2025-62399

Indicators of Compromise

• Unusually high volumes of failed authentication attempts against mobile or web service endpoints
• Multiple failed login attempts for the same user account from different IP addresses
• Automated request patterns with consistent timing intervals targeting authentication URLs
• Authentication log entries showing rapid sequential attempts from single sources

Detection Strategies

• Monitor authentication logs for anomalous patterns including high-frequency login failures
• Implement alerting on authentication endpoints receiving requests exceeding baseline thresholds
• Deploy web application firewalls with brute-force detection signatures
• Analyze traffic patterns for automated tooling characteristics such as missing user-agent headers or consistent request timing

Monitoring Recommendations

• Enable verbose logging on Moodle authentication endpoints and centralize log collection
• Configure SIEM rules to correlate failed authentication events across the platform
• Establish baseline metrics for normal authentication activity to identify deviations
• Review the Red Hat CVE-2025-62399 Advisory for additional monitoring guidance

How to Mitigate CVE-2025-62399

Immediate Actions Required

• Apply the latest Moodle security updates addressing authentication rate limiting
• Implement web application firewall rules to limit authentication request rates
• Enable account lockout policies after consecutive failed login attempts
• Consider temporarily restricting access to mobile API endpoints if patching is delayed

Patch Information

Organizations should consult official Moodle security advisories for the latest patched versions. Additional technical details are available through Red Hat Bug Report #2404432. Verify your Moodle installation version and upgrade to a patched release as soon as available.

Workarounds

• Configure reverse proxy or load balancer rate limiting for authentication endpoints
• Implement IP-based blocking for sources generating excessive failed authentication attempts
• Deploy CAPTCHA challenges on authentication forms to impede automated attacks
• Consider network-level access controls to restrict authentication endpoint access to trusted IP ranges

# Example nginx rate limiting configuration for Moodle authentication endpoints
limit_req_zone $binary_remote_addr zone=auth_limit:10m rate=5r/s;

location ~ ^/login/token\.php {
    limit_req zone=auth_limit burst=10 nodelay;
    # Additional proxy/fastcgi configuration
}

location ~ ^/webservice/rest/server\.php {
    limit_req zone=auth_limit burst=10 nodelay;
    # Additional proxy/fastcgi configuration
}