CVE-2026-61997 in Legal Stone Plugin
Summary
by MITRE • 10/29/2026
Unauthenticated PHP Object Injection in Legal Stone <= 1.2.11 versions.
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Analysis
by VulDB Data Team • 10/30/2026
The vulnerability identified as an unauthenticated PHP object injection flaw within Legal Stone versions prior to or equal to 1.2.11 represents a critical security deficiency that allows remote attackers to execute arbitrary code on the target server without requiring valid credentials. This type of vulnerability stems from the improper handling of user-supplied input during the deserialization process, where data is converted back into PHP objects in an unsafe manner. In many modern web applications, including those built with frameworks like Laravel or Symfony which Legal Stone likely utilizes, serialization is often employed to store session data, cache information, or pass complex state between requests. When these serialized strings are derived from user-controlled sources such as HTTP cookies, POST parameters, or URL query strings without sufficient validation or sanitization, an attacker can craft a malicious payload that manipulates the object properties upon deserialization.
The technical mechanism behind this exploitation relies on PHP's magic methods and registered serialization handlers. By injecting specific class names and property values into the serialized string, an attacker can trigger unintended side effects within the application logic. For instance, if the application utilizes classes with __destruct(), __wakeup(), or __toString() magic methods that perform file operations, database queries, or system command executions based on their internal state, these actions will be executed under the context of the web server process. This effectively bypasses standard authentication mechanisms because the vulnerability is triggered during the initial parsing of the request payload before any user identity verification takes place. The attacker does not need to log in; they simply send a specially crafted HTTP request containing the malicious serialized object, which the backend processes and executes immediately upon deserialization.
From an operational perspective, the impact of this vulnerability is severe and potentially catastrophic for organizations relying on Legal Stone for their legal case management or document handling needs. Successful exploitation grants the attacker full control over the underlying operating system through the web server's privileges. This can lead to complete compromise of the application environment, including access to sensitive client data stored in associated databases, theft of intellectual property, and modification of critical business records. Furthermore, this vulnerability serves as a foothold for further attacks within the network infrastructure. Attackers may use the compromised server to pivot into internal networks, deploy ransomware, or establish persistent backdoors that remain undetected by standard security monitoring tools due to their origin from legitimate application processes rather than external intrusion attempts.
This flaw aligns with CWE-502, which describes Deserialization of Untrusted Data, a category of vulnerabilities where applications fail to validate the integrity and authenticity of serialized objects before processing them. It also maps closely to MITRE ATT&CK technique T1059, specifically Command and Scripting Interpreter sub-techniques like PHP execution (T1059.007), as well as potential lateral movement vectors if the compromised server is used for further exploitation within a corporate network. The absence of authentication requirements places this vulnerability in the highest risk category according to common scoring systems such as CVSS, emphasizing its ease of exploitability and broad impact scope.
Mitigation strategies must prioritize immediate patching by upgrading Legal Stone to version 1.2.12 or later, where developers have presumably implemented strict input validation and disabled dangerous deserialization endpoints for untrusted sources. In the interim, if an upgrade is not immediately feasible, administrators should implement web application firewall rules that detect and block known patterns of PHP serialized payloads containing class names associated with vulnerable libraries. Additionally, enabling strict type checking in PHP configurations and avoiding the use of __wakeup() or other magic methods on classes that handle untrusted input can reduce the attack surface. Regular security audits focusing on serialization practices and continuous monitoring for anomalous outbound network connections from web servers are also recommended to detect potential exploitation attempts early.