CVE-2022-0441: Masterstudy LMS Auth Bypass Vulnerability

CVE-2022-0441 Overview

CVE-2022-0441 is a critical privilege escalation vulnerability in the MasterStudy LMS WordPress plugin. The plugin fails to validate certain parameters during user registration, allowing unauthenticated attackers to register new accounts with administrative privileges. This authentication bypass vulnerability enables complete compromise of affected WordPress installations without requiring any prior authentication.

Critical Impact

Unauthenticated attackers can register administrator accounts, leading to complete WordPress site takeover, data theft, malware injection, and potential lateral movement within hosted environments.

Affected Products

• MasterStudy LMS WordPress plugin versions prior to 2.7.6
• WordPress installations using vulnerable MasterStudy LMS versions
• stylemixthemes masterstudy_lms

Discovery Timeline

• 2022-03-07 - CVE-2022-0441 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-0441

Vulnerability Analysis

This vulnerability stems from inadequate input validation in the user registration functionality of the MasterStudy LMS plugin. When processing new account registrations, the plugin accepts user-controlled parameters that should be restricted to server-side enforcement only. Specifically, the plugin fails to properly validate role assignment parameters, allowing attackers to specify elevated privileges such as administrator during the registration process.

The attack is particularly dangerous because it requires no authentication and can be executed remotely over the network. An attacker can craft a malicious registration request that includes administrator role parameters, which the vulnerable plugin processes without proper authorization checks. Upon successful exploitation, the attacker gains full administrative access to the WordPress installation.

Root Cause

The root cause is improper access control (CWE-269) in the plugin's registration handler. The code fails to implement proper server-side validation for user role parameters during account creation. Instead of enforcing a default subscriber or student role and validating any role parameter against an allowlist of permitted values, the plugin directly accepts and applies the role specified in the registration request.

This design flaw violates the principle of least privilege and fails to implement defense-in-depth measures that would prevent privilege escalation during account creation.

Attack Vector

The attack is executed via network-accessible HTTP requests to the WordPress registration endpoint. An unauthenticated attacker can submit a crafted POST request to the plugin's registration functionality, including parameters that specify an administrator role.

The exploitation process involves:

1. Identifying a WordPress site running a vulnerable version of MasterStudy LMS
2. Crafting a registration request with malicious role parameters
3. Submitting the request to create an administrator account
4. Logging in with the newly created admin credentials
5. Full site compromise achieved through administrative access

Once administrative access is obtained, attackers can install malicious plugins, modify site content, extract sensitive user data, or pivot to attack the underlying server infrastructure.

Detection Methods for CVE-2022-0441

Indicators of Compromise

• Unexpected administrator accounts appearing in WordPress user lists
• User accounts created with administrator privileges without corresponding admin approval workflows
• Registration activity from suspicious IP addresses or unusual geographic locations
• Newly created admin accounts with non-standard usernames or email patterns
• Administrative actions performed by recently created accounts

Detection Strategies

• Monitor WordPress user tables for new accounts with administrator or elevated roles
• Implement alerting for any new administrator account creation events
• Review web server access logs for suspicious POST requests to registration endpoints
• Deploy Web Application Firewall (WAF) rules to detect role manipulation attempts
• Enable WordPress audit logging to track user creation and role assignment events

Monitoring Recommendations

• Configure real-time alerts for new administrator account creation
• Monitor for multiple failed login attempts followed by successful admin logins from same IP
• Review plugin update status and flag installations running MasterStudy LMS below version 2.7.6
• Implement automated vulnerability scanning for WordPress plugins on regular intervals

How to Mitigate CVE-2022-0441

Immediate Actions Required

• Update MasterStudy LMS plugin to version 2.7.6 or later immediately
• Audit existing WordPress user accounts for unauthorized administrator accounts
• Remove any suspicious or unrecognized administrator accounts
• Review recent administrative actions for signs of compromise
• Consider temporarily disabling user registration until the plugin is updated

Patch Information

The vulnerability has been addressed in MasterStudy LMS version 2.7.6. The patch implements proper server-side validation of registration parameters and enforces appropriate role restrictions during account creation. Site administrators should update to the patched version immediately.

For detailed patch information, refer to the WordPress Plugin Changeset and the WPScan Vulnerability Report.

Workarounds

• Disable user registration functionality if not required until patch is applied
• Implement IP-based access controls to restrict registration endpoint access
• Deploy Web Application Firewall rules to filter malicious registration requests
• Enable two-factor authentication for all existing administrator accounts
• Configure WordPress to require admin approval for all new user registrations

# Disable user registration in wp-config.php as temporary mitigation
# Add the following line to wp-config.php
define('DISALLOW_FILE_MODS', true);

# Or disable registration via WordPress settings
wp option update users_can_register 0

# List all administrators to audit for unauthorized accounts
wp user list --role=administrator --fields=ID,user_login,user_email,user_registered