Chapter 6.2: Hacking MCP Servers - Uncovering Vulnerabilities in Model Context Protocol (Part 2)

Описание: Welcome to Part Two of our deep dive into Model Context Protocol (MCP) security! In this episode (Chapter 6.2 of our AI and Cybersecurity learning series), we move beyond the basics (covered in Part One) and execute practical demonstrations showing how vulnerable MCP servers can be exploited.

We build an intentionally vulnerable file management MCP server to expose classic attack vectors like Command Injection and Path Traversal, emphasizing that traditional security principles remain crucial even with new technologies. We also explore risks associated with client-side LLM manipulation and the security demands of the powerful Sampling primitive.
We highlight the critical role of client-side guardrails (demonstrated by Cloud Desktop's robust protections) versus tools lacking them (like MCP Inspector).

What You Will Learn in This Video:
• Recap of MCP Fundamentals: The Model Context Protocol (MCP) simplifies M-to-N connectivity in AI applications to an M+N problem. MCP servers expose three key primitives: Resources, Tools, and Prompts.
• Command Injection Attacks: We demonstrate exploiting unvalidated user input in server-side Tools by leveraging NodeJS child process exec with shell: true. This vulnerability allowed us to inject OS commands like whoami and extract sensitive files (e.g., SSH keys).
• The Power of Client Guardrails: Watch how Cloud Desktop's security mechanisms successfully detected and blocked suspicious command chaining, while MCP Inspector (a troubleshooting tool) allowed the attacks to succeed.
• Injection via Tool Descriptions: We show how malicious or irrelevant instructions can be injected into server-supplied tool metadata, which then influences the client-side LLM's processing (e.g., generating creative haikus or security facts).
• Resource Exploitation: We explore security risks related to the Resources primitive, specifically demonstrating Directory Traversal attacks to read files outside the intended scope.
• Sampling Security Concerns: We discuss how the MCP Sampling functionality, which requests additional LLM processing from the client, requires mandatory human-in-the-loop controls and explicit user consent due to its potential risks.

Security Best Practices Highlighted:
• Input Validation: Never execute OS commands using unvalidated user input, especially when using shell execution enabled (shell: true).
• Path Sanitization: Implement strict validation and sanitization for all file paths to prevent path traversal.
• Trust Nothing: Do not trust server-supplied metadata (tool descriptions) without validation on the client side.
• Enforce Guardrails: Both MCP servers and clients must implement robust guardrails to detect and block suspicious commands or malicious inputs.
• Sampling Security: Any implementation of Sampling must enforce explicit user consent and strong security mechanisms (human-in-the-loop controls).

Code Samples: https://docs.google.com/document/d/1N...

Don't miss Part Three: We will focus entirely on implementing the necessary guardrails and security best practices to protect your MCP servers and clients.

About the Instructor:
KK Mookhey - 25+ years cybersecurity expertise. Learn MCP protocol, understand risks, build securely from day one.
Connect with KK on   / kkmookhey  

Timestamps:
0:01 — Introduction & Recap of MCP Basics
Explaining the need for MCP (M+N connectivity) and its three primitives (Resources, Tools, Prompts).
3:53 — Demonstration Setup: Vulnerable File Management Server
Building the server with shell: true to replicate a real-world command injection vulnerability (similar to a GitHub MCP server CVE).
6:46 — Command Injection Attack via MCP Inspector
Successfully injecting commands to extract system information and dummy SSH keys.
11:25 — Command Injection Attempt via Cloud Desktop
The attack is blocked by effective client-side guardrails which detect shell command chaining.
13:14 — Injection via Tool Descriptions
Manipulating the client's LLM by adding irrelevant instructions (e.g., writing a haiku about cybersecurity) into the tool metadata.
18:08 — Sampling Functionality and Security
Discussion on the security implications of Sampling and why Cloud Desktop requires human-in-the-loop security/user consent before enabling it.
20:41 — Historical Vulnerability Note
Mentioning an old remote code injection vulnerability found in MCP Inspector itself.
21:18 — Resource Exploitation & Directory Traversal Attack
Demonstrating Path Traversal to access sensitive files using the Resource primitive.
26:38 — Summary and Next Steps
Recap of the attacks and a preview of Part Three, focusing on implementing robust security guardrails.

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