CVE-2025-32223

Executive Summary

CVE-2025-32223 is an Authorization Bypass Through User-Controlled Key vulnerability in the Tutor LMS WordPress plugin by Themeum, affecting versions up to and including 3.9.4. This flaw allows an authenticated attacker (with low privileges) to manipulate user-controlled keys (e.g., user IDs, course IDs, or other object references) to access or modify resources they are not authorized to, such as other users’ course progress, grades, or private data. The vulnerability stems from improper access control checks on server-side endpoints, enabling exploitation of incorrectly configured access control security levels. As of this report, no official patch has been released, and no public exploit code or proof-of-concept is available. The CVSS score is 6.5 (Medium), with a low attack complexity and no user interaction required.

WordPress Ecosystem Context

This vulnerability is specific to the WordPress plugin ecosystem and does not affect the core WordPress software or web servers like Apache/Nginx. The issue lies entirely within the Tutor LMS plugin’s authorization logic.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): Low (L) – Attacker needs a valid user account (e.g., student).
• User Interaction (UI): None (N) – No victim action needed.
• Scope (S): Unchanged (U) – Exploit does not cross trust boundaries.
• Confidentiality (C): High (H) – Sensitive data (e.g., other users’ progress, grades) can be exposed.
• Integrity (I): None (N) – No data modification.
• Availability (A): None (N) – No denial of service.

Threat Level: Medium. While the CVSS score is 6.5, the lack of a patch and the potential for data leakage in educational environments (e.g., student records) elevates the risk for organizations using Tutor LMS.

Deep Dive & Mechanics

The vulnerability is a classic Insecure Direct Object Reference (IDOR) or Authorization Bypass Through User-Controlled Key (CWE-639). In Tutor LMS, many REST API endpoints or AJAX actions accept user-supplied identifiers (e.g., user_id, course_id, quiz_id) to fetch or modify data. The plugin fails to verify that the authenticated user has permission to access the resource associated with that key.

For example, a student user might be able to change a user_id parameter in a request to view another student’s quiz results or course completion data. The server-side code likely checks if the user is logged in but does not enforce that the requested resource belongs to that user or that the user has the appropriate role (e.g., instructor, admin) to access it.

Attack Flow:

1. Attacker logs in as a low-privileged user (e.g., student).
2. Attacker intercepts a legitimate API request (e.g., fetching their own quiz results) using a proxy like Burp Suite.
3. Attacker modifies the user_id or similar parameter to another user’s ID.
4. The server returns the target user’s data because it only validates authentication, not authorization.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common IDOR fixes.

Vulnerable Code (PHP – WordPress plugin context):

// In a REST API endpoint or AJAX handler
$user_id = $_GET['user_id'];
$results = $wpdb->get_results($wpdb->prepare("SELECT * FROM wp_tutor_quiz_attempts WHERE user_id = %d", $user_id));
return $results;

Issue: No check that $user_id matches the current user’s ID or that the user has admin/instructor privileges.

Patched Code (Hypothetical):

$user_id = intval($_GET['user_id']);
$current_user_id = get_current_user_id();
// Check if the user is an admin or instructor, or if the requested user_id is their own
if ( current_user_can('manage_options') || current_user_can('tutor_instructor') || $user_id === $current_user_id ) {
    $results = $wpdb->get_results($wpdb->prepare("SELECT * FROM wp_tutor_quiz_attempts WHERE user_id = %d", $user_id));
    return $results;
} else {
    return new WP_Error('forbidden', 'You do not have permission to access this data.', array('status' => 403));
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site with Tutor LMS <= 3.9.4 installed.
• A valid low-privileged user account (e.g., student).

Steps:

1. Log in as the student user and obtain a session cookie.
2. Use a tool like Burp Suite or curl to intercept and modify requests.
3. Identify an endpoint that accepts a user-controlled key (e.g., /wp-json/tutor/v1/quiz-attempts?user_id=123).
4. Change the user_id to another user’s ID (e.g., 456).
5. Observe the response containing the target user’s private data.

Example curl command:

curl -k -X GET "https://target-site.com/wp-json/tutor/v1/quiz-attempts?user_id=456" \
  -H "Cookie: wordpress_logged_in_xxx=student_session_cookie"

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual API requests where user_id or similar parameters are changed across multiple requests from the same session.
• Look for 403 errors followed by successful data retrieval (indicating parameter tampering).

Hardening (until patch is available):

• Implement a Web Application Firewall (WAF) rule to block requests where user_id does not match the session user ID (if feasible).
• Disable the vulnerable REST endpoints via a custom plugin or .htaccess rewrite rules.
• Restrict user roles to the minimum necessary.

Indicators of Compromise (IOCs)

• Network: HTTP requests to /wp-json/tutor/v1/* with varying user_id parameters from the same IP/session.
• Logs: WordPress debug logs showing WP_Error('forbidden', ...) or unexpected data access patterns.
• File: No specific file IOCs; this is a logic flaw.

Detection Engineering

YARA Rule

rule CVE_2025_32223_Tutor_LMS_IDOR {
    meta:
        description = "Detects potential exploitation of CVE-2025-32223 in Tutor LMS"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-32223"
    strings:
        $wp_rest = "/wp-json/tutor/v1/" ascii wide nocase
        $user_id_param = "user_id=" ascii wide nocase
        $course_id_param = "course_id=" ascii wide nocase
    condition:
        any of ($wp_rest) and any of ($user_id_param, $course_id_param)
}

Sigma Rule

title: CVE-2025-32223 Tutor LMS IDOR Exploitation Attempt
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects potential exploitation of authorization bypass in Tutor LMS
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-query|contains: 
            - '/wp-json/tutor/v1/'
        cs-uri-query|re: '(user_id|course_id|quiz_id)=\d+'
    condition: selection
falsepositives:
    - Legitimate admin/instructor actions
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-32223 Tutor LMS IDOR Exploitation Attempt";
    flow:to_server,established;
    content:"/wp-json/tutor/v1/"; http_uri;
    pcre:"/(user_id|course_id|quiz_id)=\d+/Ui";
    classtype:attempted-recon;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable vulnerable endpoints – If possible, block access to /wp-json/tutor/v1/* for non-admin users via .htaccess or a WAF.
2. Apply virtual patching – Use a WAF to inspect and block requests where user-controlled keys do not match the session user.
3. Monitor logs – Actively watch for anomalous API access patterns.

Long-term Fix:

• Update Tutor LMS – Once a patch is released (version > 3.9.4), apply it immediately.
• Code review – If you have custom code, ensure all endpoints validate authorization, not just authentication.
• Principle of least privilege – Review user roles and capabilities within Tutor LMS.

Workaround (if patching is delayed):

• Use a plugin like "User Role Editor" to restrict access to Tutor LMS REST endpoints for non-admin roles.

Valters IT – Securing digital ecosystems with precision.