CVE-2024-21746

Executive Summary

CVE-2024-21746 is an Authentication Bypass by Spoofing vulnerability in the Roxnor WP Ultimate Review WordPress plugin (versions <= 2.3.6). This flaw allows an unauthenticated attacker to spoof the identity of a legitimate user, potentially gaining unauthorized access to review-related functionality. The vulnerability is classified as CWE-290: Authentication Bypass by Spoofing and carries a CVSS score of 5.3 (Medium). No public exploit code or proof-of-concept is currently available, and the vendor has not released a patch. Given the WordPress ecosystem context, this issue affects sites running the plugin and could lead to identity spoofing attacks, such as posting fake reviews or manipulating review data.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. As a supply chain risk, any site using the plugin is exposed until a patch is applied. The plugin is not available on NPM, PyPI, Go, or Ruby ecosystems.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – Impact confined to the vulnerable component.
• Confidentiality (C): Low (L) – Limited information disclosure.
• Integrity (I): None (N) – No data modification.
• Availability (A): None (N) – No denial of service.

Threat Level: Medium. The low EPSS score (0.0%) suggests limited active exploitation, but the lack of a patch increases long-term risk.

Deep Dive & Mechanics

The vulnerability resides in the authentication mechanism of the WP Ultimate Review plugin. The plugin fails to properly validate the identity of users when processing review submissions or administrative actions. An attacker can craft HTTP requests that spoof the identity of a legitimate user (e.g., by manipulating session tokens, cookies, or nonces). This allows the attacker to perform actions that require authentication, such as submitting reviews under another user's name or modifying review settings.

The root cause is insufficient verification of the user's identity during sensitive operations. The plugin likely relies on client-supplied data (e.g., user ID in POST parameters) without server-side validation against the current session.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the plugin's authentication logic. A typical vulnerable pattern might look like:

// Vulnerable: trusts user-supplied user_id
$user_id = $_POST['user_id'];
if (is_user_logged_in()) {
    // No check that $user_id matches the logged-in user
    $review_data['author'] = $user_id;
}

A patched version would validate the user ID against the current session:

// Patched: enforce current user
$current_user = wp_get_current_user();
$user_id = $current_user->ID;
$review_data['author'] = $user_id;

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress site with WP Ultimate Review plugin <= 2.3.6.
• Knowledge of a valid user ID (e.g., admin ID=1).

Exploitation Steps:

1. Identify the vulnerable endpoint (e.g., /wp-admin/admin-ajax.php?action=submit_review).
2. Craft a POST request with a spoofed user_id parameter:

   POST /wp-admin/admin-ajax.php HTTP/1.1
   Host: target-site.com
   Content-Type: application/x-www-form-urlencoded
   
   action=submit_review&user_id=1&review_content=spoofed_review
   

3. The server processes the request as if it came from user ID 1, allowing the attacker to submit a review under the admin's identity.

Note: No public exploit code exists; this is a conceptual demonstration.

Blue Team

Detection:

• Monitor for unusual review submissions from privileged accounts (e.g., admin posting reviews).
• Log and alert on requests to admin-ajax.php with user_id parameters that differ from the authenticated user's ID.

Hunting:

• Search for HTTP requests where user_id is present in POST data and does not match the session user.
• Review database entries for reviews where author ID does not correspond to the actual session user at the time of submission.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /wp-admin/admin-ajax.php with action=submit_review and a user_id parameter.
• Logs: WordPress debug logs showing user_id mismatches.
• Database: Rows in wp_reviews table where author ID is inconsistent with expected user behavior.

Detection Engineering

YARA Rule

rule detect_wp_ultimate_review_spoofing {
    meta:
        description = "Detects potential authentication bypass in WP Ultimate Review plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-21746"
    strings:
        $s1 = "user_id" ascii wide nocase
        $s2 = "submit_review" ascii wide nocase
    condition:
        all of them
}

Sigma Rule

title: Authentication Bypass via Spoofing in WP Ultimate Review
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects attempts to exploit CVE-2024-21746 by spoofing user identity
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'admin-ajax.php'
        cs-uri-query|contains: 'action=submit_review'
        cs-uri-query|contains: 'user_id='
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-21746 WP Ultimate Review Authentication Bypass"; flow:to_server,established; content:"POST"; http_method; content:"admin-ajax.php"; http_uri; content:"action=submit_review"; http_client_body; content:"user_id="; 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 a Web Application Firewall (WAF) rule to block requests containing user_id in POST data to admin-ajax.php unless the user is authenticated and the ID matches.
3. Monitor logs for suspicious review submissions.

Long-term:

• Contact the vendor for a patch or consider replacing the plugin with an alternative.
• Apply the principle of least privilege to user roles.
• Regularly audit WordPress plugins for vulnerabilities.

Valters IT – Securing digital frontiers, one CVE at a time.