CVE-2025-5392: GB Forms DB WordPress Plugin RCE Flaw

CVE-2025-5392 Overview

A critical Remote Code Execution (RCE) vulnerability has been identified in the GB Forms DB plugin for WordPress. The vulnerability exists in the gbfdb_talk_to_front() function, which improperly handles user-supplied input by passing it directly to PHP's call_user_func() function. This dangerous code pattern allows unauthenticated attackers to execute arbitrary code on the server, potentially leading to complete site compromise, backdoor installation, or the creation of unauthorized administrator accounts.

Critical Impact
Unauthenticated attackers can achieve remote code execution on WordPress servers running vulnerable versions of GB Forms DB, enabling complete system compromise without any authentication.

Affected Products

GB Forms DB plugin for WordPress versions up to and including 1.0.2
WordPress installations with GB Forms DB plugin installed
Web servers hosting vulnerable WordPress configurations

Discovery Timeline

July 11, 2025 - CVE-2025-5392 published to NVD
July 15, 2025 - Last updated in NVD database

Technical Details for CVE-2025-5392

Vulnerability Analysis

The vulnerability stems from a code injection flaw (CWE-94) in the GB Forms DB plugin's core functionality. The gbfdb_talk_to_front() function accepts user-controlled input and passes it directly to PHP's call_user_func() without proper validation or sanitization. This function is designed to dynamically call PHP functions at runtime, but when combined with untrusted input, it becomes a dangerous attack vector.

The lack of authentication requirements means any remote attacker can exploit this vulnerability without needing valid credentials. Successful exploitation grants attackers the ability to execute arbitrary PHP code within the context of the web server, effectively giving them control over the WordPress installation and potentially the underlying server.

Root Cause

The root cause is the unsafe use of PHP's call_user_func() with user-supplied input in the gbfdb_talk_to_front() function. The vulnerable code can be found in the plugin's functions.php file. When user input is passed to call_user_func() without proper whitelisting or validation, attackers can specify arbitrary callback functions to execute, including dangerous built-in PHP functions or custom malicious callbacks.

Attack Vector

The attack is network-based and requires no authentication, user interaction, or special privileges. An attacker can craft malicious HTTP requests to the WordPress site targeting the vulnerable function endpoint. By manipulating the parameters passed to gbfdb_talk_to_front(), the attacker controls what function gets executed via call_user_func(). This can be leveraged to:

Execute system commands on the server
Install persistent backdoors in the WordPress installation
Create new administrative user accounts
Exfiltrate sensitive data from the database
Pivot to attack other systems on the network

The vulnerability details and affected code locations can be reviewed at the WordPress Plugin Function Code and the Wordfence Vulnerability Report.

Detection Methods for CVE-2025-5392

Indicators of Compromise

Unexpected administrator accounts created in WordPress with no corresponding audit trail
New or modified PHP files in the WordPress installation, particularly in plugin directories
Unusual outbound network connections from the web server
Web server access logs showing suspicious POST requests to GB Forms DB plugin endpoints
Presence of web shells or backdoor files in the wp-content directory

Detection Strategies

Monitor WordPress audit logs for unauthorized user account creation, especially administrator-level accounts
Implement file integrity monitoring on WordPress core files, themes, and plugins directories
Deploy web application firewall (WAF) rules to detect and block suspicious call_user_func exploitation patterns
Review web server access logs for anomalous requests targeting the GB Forms DB plugin endpoints
Scan for known web shell signatures and malicious PHP files

Monitoring Recommendations

Enable detailed logging on WordPress and web server access logs for forensic analysis
Configure alerting for any new administrative user account creation
Implement real-time file change monitoring on critical WordPress directories
Monitor for unusual process execution originating from the web server user context
Track outbound connections from the web server for command-and-control communication

How to Mitigate CVE-2025-5392

Immediate Actions Required

Update GB Forms DB plugin immediately to a version newer than 1.0.2 that contains the security fix
If an update is not immediately available, deactivate and remove the GB Forms DB plugin
Audit WordPress administrator accounts and remove any unauthorized entries
Scan the WordPress installation for web shells, backdoors, or unauthorized file modifications
Review server access logs for evidence of exploitation attempts

Patch Information

A security patch has been released for the GB Forms DB plugin. The fix addresses the unsafe call_user_func() usage by implementing proper input validation and function whitelisting. Site administrators should update to the latest available version immediately. The patch details can be reviewed at the WordPress Changeset Overview.

Workarounds

Temporarily disable the GB Forms DB plugin until the patch can be applied
Implement WAF rules to block requests containing suspicious callback function names
Restrict access to WordPress AJAX endpoints at the web server level if the plugin functionality is not critical
Consider using application-level firewalls to filter malicious payloads targeting the vulnerable endpoint

bash

# Disable the plugin via WP-CLI
wp plugin deactivate gb-forms-db

# Alternative: Rename the plugin directory to disable it
mv wp-content/plugins/gb-forms-db wp-content/plugins/gb-forms-db.disabled