CVE-2026-104932 in Search Regex Plugin
Summary
by MITRE • 10/16/2026
The Search Regex plugin for WordPress is vulnerable to PHP Object Injection in version 3.5 via deserialization of untrusted input in the replace_all function. This allows authenticated attackers, with subscriber-level access and above, to inject a PHP Object. The additional presence of a POP chain allows attackers to execute code.
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Analysis
by VulDB Data Team • 10/16/2026
The Search Regex plugin for WordPress, specifically version 3.5, contains a critical security flaw classified as PHP Object Injection (CWE-470). This vulnerability arises from the improper deserialization of untrusted input within the replace_all function. In typical web application architectures, functions that process user-supplied data must validate and sanitize inputs before any transformation or execution logic is applied. However, in this specific implementation, the plugin accepts serialized PHP objects directly from authenticated users without sufficient verification of their integrity or origin. This design oversight creates a direct pathway for malicious actors to manipulate internal object states by injecting crafted payloads that exploit existing class methods within the WordPress environment and its loaded plugins.
The severity of this vulnerability is significantly amplified by the presence of a Pop Chain (Prototype Pollution chain), which allows attackers to achieve Remote Code Execution (RCE). A POP chain consists of a sequence of gadget classes whose magic methods can be chained together to perform unintended actions, such as executing system commands or accessing sensitive files. When an attacker injects a serialized object that triggers these specific method calls during the deserialization process, they effectively bypass standard security controls and gain arbitrary code execution capabilities on the server hosting the WordPress instance. This transforms what might otherwise be a data manipulation issue into a full compromise of the underlying infrastructure, allowing for complete control over the web application and potentially the host system itself.
From an operational perspective, this vulnerability requires authenticated access with subscriber-level privileges or higher to exploit. While this restriction limits the attack surface compared to unauthenticated vulnerabilities, it remains highly dangerous because many WordPress sites allow public registration or have users who hold low-privilege accounts that can be easily obtained through credential stuffing, phishing, or other common attacks. Once an attacker gains even minimal access, they can leverage this flaw to escalate privileges, install backdoors, deface the website, exfiltrate sensitive database contents, or use the compromised server as a pivot point for further network intrusion. The impact extends beyond immediate code execution, potentially leading to long-term persistence and lateral movement within the organization's IT environment.
To mitigate this risk, administrators should immediately update the Search Regex plugin to the latest patched version where the deserialization issue has been resolved through proper input validation or by removing unsafe serialization practices entirely. If updating is not immediately feasible, it is advisable to disable the replace_all functionality if possible, restrict user registration on WordPress sites to trusted individuals only, and enforce strict role-based access control policies. Additionally, implementing a Web Application Firewall (WAF) with rules targeting PHP deserialization patterns can provide an additional layer of defense by blocking malicious payloads before they reach the application logic. Security teams should also monitor server logs for unusual activity indicative of exploitation attempts, such as unexpected outbound connections or file system modifications following user interactions with the plugin. Adhering to secure coding standards that prohibit the use of unserialize() on untrusted data is essential for preventing similar vulnerabilities in future development cycles. This incident underscores the importance of rigorous input validation and the dangers inherent in relying on complex gadget chains within widely used open-source ecosystems, aligning with ATT&CK techniques related to initial access via compromised credentials and execution through command and script interpretation.