CVE-2024-50526: Multi Purpose Mail Form RCE Vulnerability

CVE-2024-50526 Overview

CVE-2024-50526 is an Unrestricted Upload of File with Dangerous Type vulnerability affecting the Multi Purpose Mail Form WordPress plugin developed by Lindeni Mahlalela. This vulnerability allows unauthenticated attackers to upload arbitrary files, including web shells, to a vulnerable web server. The flaw exists due to missing file type validation in the plugin's file upload functionality, enabling remote code execution on affected WordPress installations.

Critical Impact

This vulnerability enables unauthenticated attackers to upload and execute malicious PHP web shells on vulnerable WordPress sites, leading to complete server compromise, data theft, and persistent backdoor access.

Affected Products

• Lindeni Multi Purpose Mail Form plugin for WordPress versions up to and including 1.0.2
• WordPress sites running the vulnerable multi-purpose-mail-form plugin
• All server configurations where the plugin is installed and active

Discovery Timeline

• 2024-11-04 - CVE-2024-50526 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2024-50526

Vulnerability Analysis

This vulnerability is classified under CWE-434 (Unrestricted Upload of File with Dangerous Type). The Multi Purpose Mail Form plugin fails to properly validate file types during the upload process, allowing attackers to bypass any intended restrictions and upload executable PHP files to the WordPress server.

The attack can be executed without authentication over the network, requiring no user interaction. Once a malicious file is uploaded, an attacker can execute arbitrary code on the server with the privileges of the web server process, typically leading to complete site compromise.

Root Cause

The root cause of CVE-2024-50526 lies in the plugin's failure to implement proper server-side file type validation. The upload functionality does not verify that uploaded files match expected safe types (such as images or documents), nor does it check file extensions or MIME types against a whitelist. This allows PHP files and other executable content to be uploaded directly to a web-accessible location.

Attack Vector

The vulnerability is exploited over the network (AV:N) with low attack complexity (AC:L). An attacker can target the plugin's file upload endpoint directly without any authentication or special privileges. The attack flow typically involves:

1. Identifying a WordPress site running the vulnerable Multi Purpose Mail Form plugin
2. Crafting a malicious PHP web shell or backdoor file
3. Uploading the malicious file through the plugin's unprotected upload functionality
4. Accessing the uploaded web shell via a direct URL to achieve remote code execution
5. Establishing persistence and escalating privileges on the compromised server

The vulnerability mechanism involves bypassing file upload restrictions through the plugin's mail form attachment feature. Since no server-side validation is performed, attackers can submit PHP files that are then stored in a web-accessible uploads directory. For detailed technical analysis, see the Patchstack Vulnerability Report. A proof-of-concept exploit is also available on GitHub.

Detection Methods for CVE-2024-50526

Indicators of Compromise

• Unexpected PHP files appearing in WordPress upload directories, particularly in /wp-content/uploads/ or plugin-specific folders
• Web server access logs showing POST requests to the multi-purpose-mail-form upload endpoints followed by GET requests to unusual PHP files
• Presence of files with suspicious names or double extensions (e.g., image.php, shell.php.jpg) in upload directories
• Outbound network connections from the web server to unknown external IPs

Detection Strategies

• Implement file integrity monitoring (FIM) on WordPress upload directories to detect unauthorized file additions
• Configure web application firewall (WAF) rules to inspect file uploads for PHP content and block executable file types
• Monitor web server logs for patterns consistent with web shell access, including unusual POST/GET sequences to upload directories
• Deploy endpoint detection solutions that can identify known web shell signatures and behaviors

Monitoring Recommendations

• Enable detailed logging for all file upload operations on WordPress installations
• Set up alerts for new PHP file creation in upload directories outside of normal administrative workflows
• Monitor for unusual process spawning from the web server process (e.g., www-data spawning shell commands)
• Review WordPress plugin inventory and ensure Multi Purpose Mail Form is identified and tracked

How to Mitigate CVE-2024-50526

Immediate Actions Required

• Immediately deactivate and remove the Multi Purpose Mail Form plugin from all WordPress installations
• Audit upload directories for any suspicious PHP files or recently uploaded content with executable extensions
• Review web server access logs for evidence of exploitation and investigate any suspicious activity
• Implement a web application firewall to block malicious file uploads while remediation is underway

Patch Information

As of the last update to the CVE data, no official patch has been released for this vulnerability. The affected versions include Multi Purpose Mail Form through version 1.0.2. Organizations should remove the plugin entirely until a patched version is available. For the latest information, consult the Patchstack Vulnerability Report.

Workarounds

• Remove the Multi Purpose Mail Form plugin entirely from WordPress installations until a secure version is released
• If the plugin must remain active, restrict access to upload endpoints using web server configuration rules
• Implement strict file upload validation at the web server level using .htaccess rules to deny execution of PHP files in upload directories
• Consider using alternative mail form plugins with proper security controls and active maintenance

# Configuration example - Block PHP execution in uploads directory
# Add to .htaccess in /wp-content/uploads/
<FilesMatch "\.(?:php|phtml|php[0-9])$">
    Require all denied
</FilesMatch>

# Alternative Apache configuration
<Directory "/var/www/html/wp-content/uploads">
    php_admin_flag engine Off
</Directory>