CVE-2025-3439: PHP Object Injection Vulnerability in Everest Forms WordPress Plugin

Overview

The cybersecurity landscape is riddled with threats that can compromise the integrity and confidentiality of data systems across the globe. One such vulnerability, identified as CVE-2025-3439, poses a significant threat to WordPress sites utilizing the Everest Forms plugin. This vulnerability affects all versions of the plugin up to and including 3.1.1. Given the popularity of WordPress and the extensive use of plugins to enhance its functionality, this vulnerability matters because it could potentially affect a large number of websites across the globe, leading to system compromises or data leakage.

Vulnerability Summary

CVE ID: CVE-2025-3439
Severity: Critical (CVSS Score: 9.8)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Possible system compromise or data leakage due to PHP object injection

Affected Products

Product | Affected Versions

Everest Forms WordPress Plugin | Up to and including 3.1.1

How the Exploit Works

The Everest Forms WordPress plugin is vulnerable to PHP Object Injection through the ‘field_value’ parameter. This vulnerability arises due to the plugin’s mishandling of untrusted input, which allows for the deserialization of this input. An unauthenticated attacker can exploit this flaw by injecting a malicious PHP object into the ‘field_value’ parameter. While this vulnerability does not inherently cause any harm, it can pave the way for more destructive exploits if there is a POP (Property Oriented Programming) chain present in another plugin or theme installed on the site. Depending on the POP chain, this could allow an attacker to delete arbitrary files, retrieve sensitive data, or execute malicious code.

Conceptual Example Code

Given below is a conceptual example of how the vulnerability might be exploited. This is a sample HTTP request that injects a malicious PHP object into the ‘field_value’ parameter.

POST /wp-admin/admin-ajax.php?action=everest_form_save_form_entry HTTP/1.1
Host: target.example.com
Content-Type: application/x-www-form-urlencoded
field_value=O:8:"stdClass":1:{s:5:"shell";s:9:"/bin/bash";}

In the above example, a serialized PHP ‘stdClass’ object with a ‘shell’ property is injected into the ‘field_value’ parameter. If a POP chain is present in the WordPress installation, this could potentially lead to remote code execution.

Mitigation

Users are strongly advised to apply the latest patches released by the vendor to remediate this vulnerability. If for some reason patching is not possible, users should consider implementing a Web Application Firewall (WAF) or Intrusion Detection System (IDS) to detect and block attempts to exploit this vulnerability. Regularly updating all plugins, themes, and the WordPress core installation can also help prevent the installation of software containing a POP chain.