Challenges and Strategies for the Security of the MCP System

Model Context Protocol (MCP) is currently still in the early stages of development and faces many security challenges. To help the community improve the security of MCP, Slow Mist has open-sourced the MasterMCP tool, which reveals potential risks through practical attack drills.

This article will detail common attack methods in the MCP system, including information poisoning, concealing malicious instructions, etc. All demonstration scripts have been open-sourced to GitHub, and readers can reproduce the entire process in a secure environment.

Overall Architecture Overview

Demonstration Attack Target MC:Toolbox

Toolbox is the official MCP management tool launched by a certain MCP plugin website, and the choice of it as the testing target is mainly based on the following considerations:

• The user base is large and representative.
• Supports automatic installation of other plugins to supplement certain client functions.
• Includes sensitive configurations such as API Key for demonstration purposes.

Malicious MCP Demonstration Tool: MasterMCP

MasterMCP is a simulated malicious MCP tool specifically designed for security testing, utilizing a plug-in architecture, mainly including:

1. Local Website Service Simulation
2. Local Pluginized MCP Architecture

Demo Client

• Cursor: One of the globally popular AI-assisted programming IDEs
• Claude Desktop: Official client of a certain AI company

demonstration use of large model

Choosing version Claude 3.7 represents a strong operational capability within the current MCP ecosystem.

Cross-MCP Malicious Call Demonstration

web content poisoning attack

1. Comment-based poisoning

Successfully triggered sensitive operations by embedding malicious keywords in HTML comments.

2. Encoding Type Comment Injection

Encode malicious prompts to make poisoning more covert.

Third-party API pollution attack

Directly passing the data returned from the third-party API into the context may introduce malicious payloads.

Poisoning Technique in the MCP Initialization Phase

malicious function overwrite attack

Override the original method with a function of the same name to induce the model to call a malicious function.

Add malicious global check logic

Force malicious security checks to be performed before all tools run.

Advanced Techniques for Hiding Malicious Prompts

a coding method friendly to large models

Using LLM to conceal malicious information through its parsing ability for multilingual formats:

• English Environment: Use Hex Byte Encoding
• Chinese environment: use NCR encoding or JavaScript encoding

Random Malicious Payload Return Mechanism

Each time a page with malicious payload is randomly returned, it increases the detection difficulty.

Summary

Although the MCP ecosystem is powerful, there are many security risks. From simple prompt injections to covert initialization attacks, every aspect needs to be vigilant. As large models interact more with external sources, traditional protection strategies need a comprehensive upgrade.

Developers and users should remain vigilant about the MCP system and pay attention to the details of each interaction. Only by treating it rigorously can a secure and stable MCP environment be built.

The MasterMCP script will continue to improve, open source more test cases, and help the community to deeply understand, practice, and strengthen MCP protection in a safe environment.