CVE-2025-13407: Gravity Forms WordPress Plugin RCE Flaw

CVE-2025-13407 Overview

CVE-2025-13407 is an unrestricted file upload vulnerability in the Gravity Forms plugin for WordPress. Versions prior to 2.9.23.1 fail to properly validate file types processed through the chunked upload feature. Authenticated attackers with low privileges can upload PHP files to affected sites. Successful exploitation leads to Remote Code Execution (RCE) when the attacker discovers or enumerates the upload path on the target server.

Critical Impact
Attackers with low-privilege access can upload arbitrary PHP payloads and execute code on the underlying WordPress host, compromising site integrity and confidentiality.

Affected Products

Gravity Forms WordPress plugin versions prior to 2.9.23.1
WordPress sites using Gravity Forms chunked upload functionality
Any hosting environment executing PHP files placed in the plugin's upload directory

Discovery Timeline

2025-12-24 - CVE-2025-13407 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-13407

Vulnerability Analysis

The flaw resides in the chunked upload handler of the Gravity Forms plugin. The plugin accepts file fragments and reassembles them server-side without enforcing strict validation of the resulting file extension or MIME type. This allows an authenticated user to submit a PHP file through a form configured with a file upload field.

The vulnerability is classified as an Unrestricted File Upload leading to Remote Code Execution (RCE). Exploitation requires the attacker to know or enumerate the storage path where uploaded chunks are assembled. Once the PHP file is written to a web-accessible directory, requesting it via HTTP triggers execution under the web server's user context.

Root Cause

The root cause is missing or insufficient file-type validation in the chunked upload processing routine. The plugin does not reject dangerous extensions such as .php, .phtml, or .phar before persisting the assembled file. Standard single-file upload validation controls were not applied consistently to the chunked upload code path.

Attack Vector

An attacker authenticated to the WordPress site submits a crafted request to a form that uses the file upload field with chunked upload enabled. The attacker splits a malicious PHP payload into chunks and posts them to the plugin's upload endpoint. After the server reassembles the file, the attacker locates the file within the uploads directory. Sending an HTTP request to the resulting URL invokes the PHP interpreter and executes the payload.

See the WPScan Vulnerability Report for additional technical context.

Detection Methods for CVE-2025-13407

Indicators of Compromise

Files with executable extensions (.php, .phtml, .phar, .pht) inside the wp-content/uploads/gravity_forms/ directory tree
Unexpected POST requests to Gravity Forms chunked upload endpoints from low-privilege accounts
Outbound network connections initiated by the php-fpm or web server process shortly after upload activity
New administrative WordPress accounts or modified wp-config.php timestamps following form submissions

Detection Strategies

Monitor the Gravity Forms upload directory for the creation of files with server-executable extensions
Inspect web server access logs for GET requests targeting files inside gravity_forms upload paths
Correlate authenticated form submissions with subsequent file writes to the uploads directory
Baseline expected file types accepted by production forms and alert on deviations

Monitoring Recommendations

Enable file integrity monitoring across the wp-content/uploads/ hierarchy
Forward WordPress and web server logs to a centralized SIEM for correlation and retention
Alert on process creation events where php spawns shell interpreters or network utilities
Track outbound connections from web-tier hosts to unfamiliar destinations

How to Mitigate CVE-2025-13407

Immediate Actions Required

Upgrade the Gravity Forms plugin to version 2.9.23.1 or later on all WordPress installations
Audit the wp-content/uploads/gravity_forms/ directory for unexpected PHP or script files and remove them
Rotate credentials for any WordPress accounts that may have been used to exploit the flaw
Review recent form submissions and web server logs for signs of successful exploitation

Patch Information

The vendor released Gravity Forms 2.9.23.1, which corrects the chunked upload validation logic. Refer to the WPScan Vulnerability Report for advisory details. Apply the update through the WordPress plugin manager or by replacing the plugin files with the patched release.

Workarounds

Disable the chunked upload feature on Gravity Forms file upload fields until the patch is applied
Restrict form submission capabilities to trusted user roles only
Configure the web server to deny PHP execution inside the wp-content/uploads/ directory
Deploy a web application firewall (WAF) rule blocking uploads with executable extensions

bash

# Apache: deny PHP execution inside the WordPress uploads directory
# Place this .htaccess file at wp-content/uploads/.htaccess
<FilesMatch "\.(php|phtml|phar|pht|php[0-9])$">
    Require all denied
</FilesMatch>

# Nginx equivalent (server block)
location ~* /wp-content/uploads/.*\.(php|phtml|phar|pht)$ {
    deny all;
    return 403;
}