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How CVE-2025-3439 Works
The vulnerability exists in the Everest Forms WordPress plugin (≤ v3.1.1) due to insecure deserialization of user-supplied input in the `field_value` parameter. Attackers can craft malicious serialized PHP objects and inject them via form submissions. When the plugin deserializes this data, it triggers unintended object instantiation. While no viable Property-Oriented Programming (POP) chain exists in Everest Forms alone, combining this flaw with another plugin/themes POP chain enables remote code execution (RCE), file deletion, or data theft. The absence of proper input validation and unsafe `unserialize()` usage allows this exploit.
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Platform: WordPress
Version: ≤ 3.1.1
Vulnerability: PHP Object Injection
Severity: Critical
Date: 04/23/2025
What Undercode Say:
Exploitation (PoC):
- Craft malicious serialized payload (replace `
` with gadget chain): [bash] $payload = serialize([bash]);
2. Send payload via form submission:
POST /wp-admin/admin-ajax.php HTTP/1.1 Host: target.com Content-Type: application/x-www-form-urlencoded action=everest_forms_ajax&field_value=<?php echo urlencode($payload); ?>
Detection:
- Check plugin version:
SELECT option_value FROM wp_options WHERE option_name = 'everest_forms_version';
- Log analysis for suspicious `unserialize()` calls:
grep -r "unserialize.field_value" /var/www/html/
Mitigation:
1. Immediate actions:
Remove vulnerable plugin wp plugin delete everest-forms
2. WAF rule to block exploits:
location ~ admin-ajax.php {
if ($args ~ "field_value=[^;]+;") {
return 403;
}
}
3. PHP hardening:
; Disable unserialize() disable_functions = unserialize
References:
- Patch: Upgrade to Everest Forms ≥ 3.1.2
- Advisory: Wordfence CVE-2025-3439
- CVSS 4.0: `CVSS:4.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
