CVE-2025-8871 is a deserialization vulnerability categorized under CWE-502 affecting the Everest Forms Pro plugin for WordPress, specifically all versions up to 1.9.7. The flaw arises from unsafe deserialization of untrusted input within the mime_content_type() function, enabling PHP Object Injection. An unauthenticated attacker can exploit this vulnerability if a form on the site contains both a non-required signature field and an image upload field. However, the vulnerability alone does not allow direct exploitation because no gadget POP (Property Oriented Programming) chain is present within Everest Forms Pro itself. Successful exploitation depends on the presence of additional plugins or themes installed on the WordPress site that contain a POP chain, which can be leveraged to perform malicious actions such as arbitrary file deletion, sensitive data retrieval, or remote code execution. The vulnerability is limited to environments running PHP versions prior to 8, as PHP 8 introduced changes that mitigate this attack vector. The CVSS 3.1 base score is 5.6, indicating a medium severity with network attack vector, high attack complexity, no privileges required, no user interaction, and limited impact on confidentiality, integrity, and availability. No known exploits are currently in the wild, and no patches have been linked yet, though the vulnerability was published in November 2025. This issue highlights the risk of insecure deserialization combined with the presence of gadget chains in WordPress ecosystems, emphasizing the need for careful plugin and theme management.

For European organizations, the impact of CVE-2025-8871 depends heavily on their WordPress environment configuration. Organizations using Everest Forms Pro on PHP versions prior to 8 and having forms with the specified fields are at risk if their WordPress installation includes other plugins or themes that provide exploitable POP chains. Potential impacts include unauthorized deletion of files, exposure of sensitive data, or remote code execution, which could lead to website defacement, data breaches, or full system compromise. This could disrupt business operations, damage reputation, and lead to regulatory non-compliance under GDPR if personal data is exposed. The medium severity score reflects that exploitation is not straightforward and requires a specific environment setup, but the consequences can be severe if exploited. Organizations running PHP 8 or higher are not vulnerable, reducing risk. Since no public exploits are known, the threat is currently theoretical but warrants proactive mitigation to prevent future attacks.

European organizations should take a multi-layered approach to mitigate this vulnerability. First, upgrade PHP to version 8 or later, as this vulnerability is not exploitable on these versions. Second, audit all installed WordPress plugins and themes for known POP chains or unsafe deserialization practices, removing or updating any that pose a risk. Third, restrict or disable the use of non-required signature fields and image upload fields in forms where possible to reduce the attack surface. Fourth, monitor WordPress sites for unusual file deletions, data access patterns, or code execution attempts. Fifth, implement strict file permissions and web application firewall (WAF) rules to detect and block suspicious deserialization payloads. Finally, maintain regular backups and have an incident response plan ready to quickly recover from any compromise. Organizations should also track updates from WPEverest for patches addressing this vulnerability and apply them promptly once available.