CVE-2023-6559: MW WP Form Path Traversal Vulnerability

CVE-2023-6559 Overview

The MW WP Form plugin for WordPress contains a critical arbitrary file deletion vulnerability affecting all versions up to and including 5.0.3. This security flaw stems from improper validation of file paths during the file deletion process, allowing unauthenticated attackers to delete arbitrary files on the affected WordPress installation. The vulnerability is classified as a Path Traversal weakness (CWE-22), enabling attackers to manipulate file paths to access and delete files outside the intended directory structure.

Critical Impact

Unauthenticated attackers can delete critical WordPress files including wp-config.php, potentially leading to complete site takeover and remote code execution.

Affected Products

• MW WP Form plugin for WordPress versions up to and including 5.0.3
• Web-soudan MW WP Form (all installations prior to the security patch)

Discovery Timeline

• 2023-12-16 - CVE-2023-6559 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-6559

Vulnerability Analysis

This vulnerability represents a critical path traversal flaw in the MW WP Form WordPress plugin's file handling mechanism. The plugin fails to properly validate and sanitize file paths when processing file deletion requests. This oversight allows malicious actors to craft requests containing directory traversal sequences (such as ../) to navigate outside the intended upload directory and target any file accessible to the web server process.

The most significant impact of this vulnerability is the ability to delete the wp-config.php file, which contains database credentials and WordPress security keys. Deletion of this file forces WordPress into a reinstallation state, potentially allowing an attacker to reconfigure the site with their own database and administrative credentials.

Root Cause

The root cause of CVE-2023-6559 lies in the insufficient input validation within the MW WP Form plugin's file deletion functionality. The plugin accepts user-supplied file paths without properly sanitizing or validating them against path traversal attempts. Specifically, the code fails to:

1. Canonicalize the file path to resolve directory traversal sequences
2. Verify that the target file resides within the expected upload directory
3. Implement proper access controls before executing file deletion operations

This allows the unlink() or equivalent file deletion function to operate on arbitrary files accessible to the PHP process.

Attack Vector

The attack is network-based and requires no authentication, making it particularly dangerous for publicly accessible WordPress installations. An attacker can exploit this vulnerability by:

1. Identifying a WordPress site running a vulnerable version of MW WP Form
2. Crafting a malicious request to the plugin's file handling endpoint
3. Including path traversal sequences in the file parameter to target critical WordPress files
4. Executing the request to delete the targeted file

The vulnerability can be exploited remotely through crafted HTTP requests to the WordPress installation. By targeting the wp-config.php file located in the WordPress root directory, an attacker can trigger a WordPress reinstallation workflow and potentially gain administrative access to the compromised site. Technical details and patch information are available in the WordPress Plugin Changeset and Wordfence Vulnerability Report.

Detection Methods for CVE-2023-6559

Indicators of Compromise

• Unexpected deletion of WordPress core files, particularly wp-config.php
• WordPress installation prompts appearing on previously configured sites
• Web server error logs showing 404 errors for critical configuration files
• Unusual HTTP requests to MW WP Form plugin endpoints containing path traversal patterns (../)
• Database connection errors following suspicious web traffic

Detection Strategies

• Monitor web server access logs for requests containing directory traversal sequences (../, ..%2f, ..%5c) targeting the MW WP Form plugin
• Implement file integrity monitoring (FIM) on critical WordPress files including wp-config.php, .htaccess, and index.php
• Deploy web application firewall (WAF) rules to detect and block path traversal attempts
• Configure alerts for any file deletion activity originating from PHP processes in the WordPress directory

Monitoring Recommendations

• Enable and review WordPress debug logging to capture suspicious plugin activity
• Implement real-time monitoring of file system changes in the WordPress installation directory
• Set up alerts for HTTP requests with anomalous path patterns targeting plugin endpoints
• Review web server logs regularly for signs of enumeration or exploitation attempts

How to Mitigate CVE-2023-6559

Immediate Actions Required

• Update MW WP Form plugin to the latest patched version immediately
• Audit file system for any unauthorized deletions or modifications
• Review web server logs for indicators of prior exploitation attempts
• Temporarily disable the MW WP Form plugin if immediate update is not possible
• Implement WAF rules to block path traversal attempts as a defense-in-depth measure

Patch Information

The vulnerability has been addressed by the plugin developers. The security patch is available through the WordPress Plugin Changeset. Site administrators should update to a version greater than 5.0.3 through the WordPress admin dashboard or by manually updating the plugin files.

Workarounds

• Disable the MW WP Form plugin until the patch can be applied
• Implement server-level file permission restrictions to protect critical WordPress files
• Deploy a web application firewall (WAF) with rules to block path traversal patterns
• Restrict write permissions on wp-config.php and other critical files at the operating system level
• Consider using security plugins that provide virtual patching capabilities

# Protect critical WordPress files with restrictive permissions
chmod 400 wp-config.php
chown root:root wp-config.php

# Add .htaccess rules to block path traversal attempts
echo 'RewriteEngine On' >> .htaccess
echo 'RewriteCond %{QUERY_STRING} (\.\./|\.\.) [NC]' >> .htaccess
echo 'RewriteRule .* - [F,L]' >> .htaccess