Description

Editor PHP Object Injection in Ultimate Addons for Contact Form 7 <= 3.5.51 versions.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.2",
  "pubDate": "2026-09-30T13:17:33.153Z",
  "pubdate": "2026-09-30T13:17:33.153Z",
  "executiveSummary": "The Ultimate Addons for Contact Form 7 plugin, specifically versions 3.5.51 and below, contains a critical PHP Object Injection vulnerability.\nThis security flaw allows an unauthenticated or authenticated attacker to pass malicious serialized data to vulnerable application functions, resulting in the instantiation of arbitrary PHP objects.\nThe primary risk implication involves remote code execution (RCE), unauthorized data manipulation, or denial-of-service, depending on the available gadget chains present within the application's environment.\nBy manipulating the serialized input, an attacker can influence the state of the application, potentially hijacking the control flow and executing unauthorized code with the privileges of the web server process.\nThe vulnerability is inherent to the improper handling of user-supplied serialized input, which lacks sufficient validation or sanitization prior to the deserialization process.\nGiven the severity of potential RCE, this vulnerability poses a critical threat to the confidentiality, integrity, and availability of the host web application.",
  "technicalDetails": "The vulnerability originates from the insecure use of the PHP unserialize() function on untrusted user-supplied input within the Ultimate Addons for Contact Form 7 plugin.\nIn PHP, the unserialize() function converts a stored representation of an object back into a PHP object. If the application environment contains 'gadget chains'—existing classes with 'magic methods' such as __destruct(), __wakeup(), or __toString()—an attacker can leverage these methods to execute arbitrary code or perform unintended actions when the object is instantiated.\nThe attack flow begins when an attacker identifies an entry point within the plugin where serialized data is accepted as an input parameter (e.g., via HTTP GET or POST requests).\nBy crafting a malicious payload, the attacker can supply a serialized object that, when unserialized, triggers the execution of unintended code paths defined in the application's codebase or within loaded third-party libraries.\nBecause the plugin fails to perform adequate signature verification or validation on the serialized string, it blindly trusts the input provided by the user.\nWhen the vulnerable function processes this input, it instantiates the malicious object. The magic methods defined within the gadget chain are triggered, allowing the attacker to bypass access controls, overwrite application state, or achieve remote code execution (RCE) by manipulating property values of the object.\nThe scope of exploitation is limited by the presence and availability of suitable gadget chains in the application. In many WordPress environments, the combination of the plugin with core functionality or other active plugins significantly increases the probability of finding a viable gadget chain.\nSince this process occurs server-side, the vulnerability is fully network-exploitable. The attacker does not necessarily require administrative privileges to initiate the exploit, provided the vulnerable endpoint is accessible via the web interface.\nSuccessful exploitation results in full compromise of the application, potentially leading to total data exfiltration, injection of persistent web shells, or lateral movement within the hosting infrastructure."
}