x64dbg-MCP Server Patch Fixes Critical Unauthenticated Remote Code Execution Flaw

A critical security vulnerability in the x64dbg-MCP Server plugin for the x64dbg debugger has been patched, resolving a flaw that allowed unauthenticated remote code execution. The issue, tracked as CVE-2026-107824, affects all versions of the plugin prior to 1.1 and has been assigned a CVSS score of 9.3, indicating a critical severity level.

The vulnerability stems from the plugin’s default configuration, which exposes the debugger’s full functionality over HTTP without requiring authentication. The x64dbg-MCP Server is a native Model Context Protocol (MCP) plugin designed to integrate the debugger with AI models and other tools. However, before version 1.1, the server listened on 0.0.0.0 by default, making it accessible to any network client that could reach the service. This default binding meant that the service was exposed to the entire local network and potentially beyond, depending on the host’s firewall configuration.

Exploitation Mechanics and Impact

An attacker who could reach the default ports—9094 for x64 or 9095 for x32—could interact with the MCP debugger tools without any form of authentication. According to the National Vulnerability Database (NVD), this lack of access control allowed unauthenticated clients to execute arbitrary x64dbg commands.

The potential impact of this vulnerability is severe. Attackers could attach to running processes by their Process ID (PID), read and write to the memory of the debuggee, and write files to arbitrary paths on the host system. This level of access effectively grants an attacker full control over the debugging session and the ability to manipulate the target application’s state or persist malware on the system. The weakness is categorized under CWE-306, which relates to incorrect default permissions, highlighting the risk of exposing sensitive interfaces without proper security controls by default.

Affected Software and Remediation

The vulnerability affects the x64dbg-mcp-server developed by duty1g. Specifically, any version of the software prior to 1.1 is vulnerable. The issue has been addressed in version 1.1, which introduces necessary authentication mechanisms to prevent unauthorized access to the debugger’s functionalities.

Users of the x64dbg debugger who have installed the MCP Server plugin are advised to update to version 1.1 immediately. The update ensures that the plugin no longer exposes its tools over HTTP and SSE without authentication, thereby mitigating the risk of remote exploitation. Given the default network exposure of the previous versions, systems that had the plugin installed and running on a networked machine were at significant risk of compromise if the ports were accessible to external actors.

What should you do?

Security professionals and developers using the x64dbg debugger should verify their current version of the x64dbg-MCP Server. If the version is below 1.1, an immediate update is required to patch the authentication bypass. Additionally, users should audit their network configurations to ensure that debugging tools are not exposed to untrusted networks. Restricting access to the default ports (9094 and 9095) through firewall rules can provide an additional layer of defense, even after patching. Monitoring for unexpected connections to these ports can also help detect potential exploitation attempts.