The recently released Damn Vulnerable Model Context Protocol (DVMCP) project has sparked significant discussion within the tech community about the security implications of Model Context Protocol (MCP) implementations. This educational project, designed to showcase vulnerabilities in MCP implementations, has highlighted a fundamental misunderstanding about how these systems should be deployed and secured.
Trust Boundaries Are Key to MCP Security
MCP servers, according to experts in the comment threads, are not designed to be public-facing APIs but rather components that operate within trusted environments. Many commenters emphasize that MCP assumes its transport layer is inherently trusted, which isn't widely understood by developers implementing these systems. One commenter noted that the protocol makes this clear through its default stdio transport mechanism, indicating MCP servers are expected to run in environments that are implicitly trustworthy for any client that can reach them.
The MCP spec makes it pretty clear that MCP servers are expected to be run in environments that are implicitly trusted/trustable for any client that can reach them. This is clear from the default/assumed stdio transport, but even with SSE the protocol expects auth to be already-solved.
This perspective frames MCP servers not as standalone services but as client applications themselves—essentially proxies or gateways that abstract services and add context for LLMs to interact with them.
Real-World Security Incidents Raise Concerns
Despite the theoretical security model, real-world implementations have already demonstrated significant vulnerabilities. Security researchers from Invariant Labs have documented several attack vectors including tool poisoning, rug pulls, and tool shadowing. One particularly concerning example involved a WhatsApp MCP server that could give attackers access to private data through social engineering techniques, where attackers could text users with instructions for their assistant to forward private messages to another account.
These incidents suggest that while MCP may not be inherently vulnerable, the ecosystem currently encourages implementations that can lead to security breaches. The gap between the theoretical security model (where MCP operates in a trusted environment) and practical implementations (where security boundaries are often poorly defined) appears to be the root of many vulnerabilities.
Security Resources for MCP
- Initial Security Note: https://invariantlabs.ai/blog/mcp-security-notification-tool... (Details on Tool Poisoning, Rug Pulls, Tool Shadowing)
- WhatsApp MCP Exploit: https://invariantlabs.ai/blog/whatsapp-mcp-exploited
- BrowserMCP Attack: https://x.com/lbeurerkellner/status/1912145060763742579
- Security Scanning Tool: https://github.com/invariantlabs-ai/mcp-scan
Proper Implementation Requires Clear Boundaries
Developers who have successfully implemented secure MCP servers emphasize the importance of explicit controls. One commenter described creating a server with strict limitations on what it could do—for example, allowing it to send mail but only to specific email addresses, or restricting file system access to non-confidential directories. This approach treats the MCP server as having the same permissions and access as the person talking to the LLM, establishing a clear security boundary.
The DVMCP project itself outlines ten challenges across three difficulty levels, demonstrating various attack vectors from basic prompt injection to sophisticated multi-vector attacks. These educational examples serve as warnings about what can go wrong when security considerations are overlooked in MCP implementations.
Key MCP Security Vulnerabilities Demonstrated in DVMCP
- Prompt Injection: Manipulating LLM behavior through malicious inputs
- Tool Poisoning: Hiding malicious instructions in tool descriptions
- Excessive Permissions: Exploiting overly permissive tool access
- Rug Pull Attacks: Exploiting tool definition mutations
- Tool Shadowing: Overriding legitimate tools with malicious ones
- Indirect Prompt Injection: Injecting instructions through data sources
- Token Theft: Exploiting insecure token storage
- Malicious Code Execution: Executing arbitrary code through vulnerable tools
- Remote Access Control: Gaining unauthorized system access
- Multi-Vector Attacks: Combining multiple vulnerabilities
Educational Tools Face Distribution Challenges
Interestingly, some commenters also raised concerns about the project's name, noting that the word Damn in Damn Vulnerable Model Context Protocol could limit its adoption in educational settings, particularly for K-12 students. This mirrors challenges faced by the similarly-named Damn Vulnerable Web Application (DVWA), where educators have had to rename or clone the project to make it appropriate for younger students.
As MCP adoption grows, the community appears to be grappling with both technical security challenges and practical considerations for how to educate the next generation of developers about these issues. The DVMCP project, despite potential naming concerns, represents an important step in raising awareness about security considerations in this emerging protocol.
The discussions around MCP security highlight a critical point for developers: understanding the intended deployment context and security model of a protocol is just as important as understanding its technical specifications. As one commenter succinctly put it, MCP security is all about trust—if you trust it, you're fine, but that trust needs to be established through proper implementation and clear boundaries.