CVE-2026-112851 in HotLock Plugin
Summary
by MITRE • 10/23/2026
Deserialization of Untrusted Data vulnerability in ThemeREX Group HotLock hotlock allows Object Injection.This issue affects HotLock: from n/a through 1.3.9.
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Analysis
by VulDB Data Team • 10/23/2026
The identified security flaw represents a critical deserialization of untrusted data vulnerability within the ThemeREX Group HotLock plugin, specifically affecting versions ranging from no initial version up to release 1.3.9. This category of vulnerability arises when an application accepts serialized objects from external sources without adequate validation or sanitization before processing them. In this specific context, the flaw manifests as object injection, allowing attackers to manipulate the internal state of the application by injecting maliciously crafted PHP objects that are subsequently deserialized and executed within the server environment. This mechanism bypasses standard input filtering mechanisms because the vulnerability lies not in how data is entered but in how it is interpreted and instantiated by the underlying runtime engine.
From a technical perspective, this issue aligns with CWE-502, which describes Deserialization of Untrusted Data. The core problem involves the use of PHP's unserialize function or similar deserialization routines on input that originates from users or external APIs without sufficient integrity checks. When an attacker provides a serialized object containing malicious payloads, such as those leveraging public gadgets found in commonly used libraries like Guzzle or SwiftMailer, they can trigger arbitrary code execution during the unserialization process. This is often facilitated through PHP's magic methods, which are automatically invoked when objects are created or destroyed, allowing for side effects that lead to remote command execution, file inclusion, or database manipulation depending on the available gadget chain and server configuration.
The operational impact of this vulnerability is severe, as it effectively grants an attacker full control over the affected WordPress site if they can trigger the vulnerable code path. Depending on the hosting environment's permissions, this could result in complete compromise of the web server, leading to data exfiltration, defacement, or the installation of backdoors and malware for persistent access. Attackers do not necessarily need high-level privileges to exploit this; even low-privileged user accounts with access to specific plugin features that trigger deserialization can potentially execute arbitrary code on the backend. This transforms a seemingly minor configuration issue into a critical security breach capable of undermining the entire infrastructure hosting the application.
In terms of threat modeling, this vulnerability is frequently associated with ATT&CK technique T1059, Command and Scripting Interpreter, as it enables attackers to run system commands through the compromised application layer. It also relates to T1190, Exploit Public-Facing Application, since plugins are often exposed directly to internet traffic. The exploitation typically involves crafting a serialized payload that exploits known gadget chains within PHP libraries included by the plugin or its dependencies. Once executed, this allows for lateral movement within the network if the server is part of a larger cluster, making prompt remediation essential to prevent broader infrastructure compromise.
Mitigation strategies must prioritize immediate patching and defensive coding practices. The most effective solution is to upgrade HotLock to version 1.3.9 or later where the vendor has presumably addressed this issue by implementing strict input validation, using whitelisting for allowed classes during deserialization, or replacing unsafe serialization functions with safer alternatives like JSON encoding/decoding which do not support object instantiation. For organizations unable to patch immediately due to compatibility constraints, applying a web application firewall rule that detects and blocks common PHP serialized payload patterns can provide temporary protection. Additionally, disabling the unserialize function in php.ini for environments where it is not strictly necessary serves as a strong defense-in-depth measure against this class of attacks. Regular security audits and code reviews focusing on data handling routines are recommended to prevent similar vulnerabilities from being introduced in future updates or other plugins within the ecosystem.