critical CVSS 9.8

CVE-2025-3439·PHP vulnerability

The Everest Forms – Contact Form, Quiz, Survey, Newsletter & Payment Form Builder for WordPress plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 3.1.1 via deserialization of untrusted input from the 'field_value' parameter. This makes it possible for unauthenticated attackers to inject a PHP Object. No known POP chain is present in the vulnerable software, which means this vulnerability has no impact unless another plugin or theme containing a POP chain is installed on the site. If a POP chain is present via an additional plugin or theme installed on the target system, it may allow the attacker to perform actions like delete arbitrary files, retrieve sensitive data, or execute code depending on the POP chain present.

Severity
critical
Software
PHP
Fixed in
3.1.2
Published
2025-04-11

Affected versions

Until: 3.1.2

Fixed in: 3.1.2

How to fix this CVE

Update the Everest Forms WordPress plugin to version 3.1.2 or later to patch the PHP Object Injection vulnerability. This update eliminates unsafe deserialization of untrusted input from the 'field_value' parameter. While exploitation requires a secondary POP chain to be present, upgrading immediately reduces your attack surface and removes the injection vector entirely.

sudo dnf update php

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST /wp-admin/admin-ajax.php.*field_value.*O:[0-9]+:".*":.*{.*}

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Block POST requests to form handlers containing base64-encoded or URL-encoded serialized PHP objects in the 'field_value' parameter. Implement input validation to reject data containing serialization markers (e.g., 'O:', 'a:', 'C:') in form fields.

How to check if you are affected

  1. Step 1: Check the installed Everest Forms plugin version by running: wp plugin list --field=name,version | grep everest-forms (requires WP-CLI access)
  2. Step 2: Verify if additional plugins with POP chains are installed by reviewing wp-content/plugins/ directory and cross-referencing against known vulnerable packages
  3. Step 3: Search web server logs for POST requests to admin-ajax.php or form endpoints containing base64-encoded serialized objects in the 'field_value' parameter: grep -i 'field_value.*O:' /var/log/apache2/access.log
  4. Step 4: Confirm the fix by verifying Everest Forms version is 3.1.2 or higher via the WordPress admin dashboard or wp plugin list command

FAQ

What is CVE-2025-3439?

CVE-2025-3439 is a PHP Object Injection vulnerability in the Everest Forms WordPress plugin that allows unauthenticated attackers to inject malicious PHP objects through the 'field_value' parameter. The vulnerability depends on a secondary POP (Property-Oriented Programming) chain from another plugin or theme to achieve code execution or data theft.

Is CVE-2025-3439 being actively exploited?

No, CVE-2025-3439 is not currently listed on the CISA KEV catalog and has no known public exploits available. However, the critical CVSS 9.8 score warrants immediate patching as exploit code could emerge.

What versions of Everest Forms are affected by CVE-2025-3439?

All versions of Everest Forms up to and including 3.1.1 are affected. The vulnerability has been patched in version 3.1.2 and later.

How do I check if my server is vulnerable to CVE-2025-3439?

Use wp plugin list --field=name,version | grep everest-forms to check your installed version. If it shows 3.1.1 or earlier, your site is vulnerable. Additionally, audit installed plugins for known POP chain vulnerabilities using security scanners like Wordfence or Sucuri.

Does Defensia detect CVE-2025-3439?

Yes — Defensia's CVE advisory scanner compares installed WordPress plugin versions against the NVD database. If Everest Forms is installed on a monitored server, CVE-2025-3439 will appear in your dashboard with remediation steps.

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References

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