CVE-2025-3515: Contact Form 7 File Upload RCE Flaw

CVE-2025-3515 Overview

CVE-2025-3515 is a critical arbitrary file upload vulnerability affecting the Drag and Drop Multiple File Upload for Contact Form 7 plugin for WordPress. The vulnerability exists due to insufficient file type validation in all versions up to and including 1.3.8.9. This security flaw allows unauthenticated attackers to bypass the plugin's blacklist protection and upload malicious file types, including .phar files, to the affected site's server.

The vulnerability is particularly dangerous on servers configured to handle .phar files as executable PHP scripts, such as default Apache+mod_php configurations where the file extension is not strictly validated before being passed to the PHP interpreter. Successful exploitation could lead to remote code execution, enabling attackers to gain complete control over the affected WordPress installation.

Critical Impact

Unauthenticated attackers can upload malicious .phar files to achieve remote code execution on vulnerable WordPress sites running Apache+mod_php configurations, potentially leading to complete server compromise.

Affected Products

• Codedropz Drag and Drop Multiple File Upload - Contact Form 7 versions up to and including 1.3.8.9
• WordPress sites using vulnerable plugin versions with Apache+mod_php configurations
• Servers configured to execute .phar files as PHP scripts

Discovery Timeline

• 2025-06-17 - CVE-2025-3515 published to NVD
• 2025-08-11 - Last updated in NVD database

Technical Details for CVE-2025-3515

Vulnerability Analysis

This arbitrary file upload vulnerability (CWE-434) stems from inadequate file type validation in the plugin's upload handling functionality. The core issue lies in the plugin's reliance on a blacklist-based approach for filtering dangerous file extensions, which can be circumvented by uploading file types not explicitly blocked, such as .phar archives.

The vulnerability is exploitable without authentication, meaning any remote attacker can craft and submit malicious files through the Contact Form 7 file upload interface. When the uploaded .phar file is accessed on a server that processes .phar extensions as PHP code, the attacker achieves arbitrary code execution within the web server's context.

Root Cause

The root cause of this vulnerability is the insufficient file type validation mechanism in the dnd-upload-cf7.php file. The plugin implements a blacklist approach to prevent dangerous file uploads, but fails to account for all potentially executable file types. The .phar extension, which can contain executable PHP code, was not included in the blacklist, allowing attackers to bypass the intended security controls.

The vulnerable code path does not perform comprehensive validation of file contents or enforce strict allowlist-based filtering, instead relying on extension checking that can be evaded through the use of alternative PHP-executable file formats.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by submitting a crafted form containing a malicious .phar file through any page that uses the Contact Form 7 plugin with the vulnerable Drag and Drop Multiple File Upload extension.

The attack flow involves crafting a .phar archive containing malicious PHP code, submitting the file through the vulnerable upload endpoint while bypassing the blacklist filter, and then accessing the uploaded file directly to trigger code execution on servers configured to process .phar files.

For technical details on the vulnerable code path, refer to the WordPress Plugin Code Snippet.

Detection Methods for CVE-2025-3515

Indicators of Compromise

• Presence of unexpected .phar files in WordPress upload directories, particularly in /wp-content/uploads/ subdirectories
• Web server access logs showing requests to .phar files in upload directories
• Unusual PHP processes or shell commands spawned by the web server process
• New or modified files in WordPress directories with recent timestamps that don't correspond to legitimate administrative actions

Detection Strategies

• Monitor file system events for creation of .phar files in WordPress upload directories using file integrity monitoring tools
• Implement web application firewall (WAF) rules to detect and block file upload requests containing .phar extensions
• Review web server access logs for POST requests to Contact Form 7 endpoints followed by GET requests to uploaded files with suspicious extensions
• Deploy endpoint detection solutions to identify post-exploitation activity such as reverse shells or command execution

Monitoring Recommendations

• Enable detailed logging for file uploads in WordPress and analyze logs for anomalous file types
• Configure alerts for any .phar, .php, or other executable file types appearing in upload directories
• Implement real-time file integrity monitoring on the WordPress installation directory
• Monitor for outbound network connections from the web server that may indicate command and control communication

How to Mitigate CVE-2025-3515

Immediate Actions Required

• Update the Drag and Drop Multiple File Upload for Contact Form 7 plugin to version 1.3.8.10 or later immediately
• Audit upload directories for any suspicious .phar files and remove unauthorized uploads
• Review web server logs for evidence of exploitation attempts and investigate any successful uploads
• Consider temporarily disabling the plugin if immediate patching is not possible

Patch Information

Codedropz has released a security patch addressing this vulnerability. The fix is available in the WordPress Plugin Changeset. Users should update to the latest version through the WordPress admin dashboard or by downloading the patched version directly from the WordPress plugin repository.

Additional vulnerability details and remediation guidance are available in the Wordfence Vulnerability Report.

Workarounds

• Configure the web server to prevent execution of .phar files by adding appropriate handler directives in Apache or nginx configuration
• Implement a web application firewall rule to block uploads with .phar extensions at the perimeter
• Restrict the plugin's allowed file types to a strict allowlist of only necessary and safe file extensions
• Disable file upload functionality in Contact Form 7 if not required for business operations

# Apache configuration to block .phar execution
# Add to .htaccess or Apache configuration file
<FilesMatch "\.phar$">
    SetHandler none
    ForceType text/plain
</FilesMatch>

# Deny access to upload directories for PHP files
<Directory "/var/www/html/wp-content/uploads">
    php_admin_flag engine off
</Directory>