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Show HN: MCP-Shield – Detect security issues in MCP servers

(github.com)
134 points nick_wolf | 2 comments | 15 Apr 25 05:15 UTC | HN request time: 0.528s | source

I noticed the growing security concerns around MCP (https://news.ycombinator.com/item?id=43600192) and built an open source tool that can detect several patterns of tool poisoning attacks, exfiltration channels and cross-origin manipulations.

MCP-Shield scans your installed servers (Cursor, Claude Desktop, etc.) and shows what each tool is trying to do at the instruction level, beyond just the API surface. It catches hidden instructions that try to read sensitive files, shadow other tools' behavior, or exfiltrate data.

Example of what it detects:

- Hidden instructions attempting to access ~/.ssh/id_rsa

- Cross-origin manipulations between server that can redirect WhatsApp messages

- Tool shadowing that overrides behavior of other MCP tools

- Potential exfiltration channels through optional parameters

I've included clear examples of detection outputs in the README and multiple example vulnerabilities in the repo so you can see the kinds of things it catches.

This is an early version, but I'd appreciate feedback from the community, especially around detection patterns and false positives.

Show context
Manfred ◴[15 Apr 25 07:57 UTC] No.43690137[source]▶
People have been struggling with securing against SQL injection attacks for decades, and SQL has explicit rules for quoting values. I don't have a lot of faith in finding a solution that safely includes user input into a prompt, but I would love to be proven wrong.
replies(3): >>43690202 #>>43690816 #>>43693274 #
jason-phillips ◴[15 Apr 25 08:09 UTC] No.43690202[source]▶
> People have been struggling with securing against SQL injection attacks for decades.

Parameterized queries.

A decades old struggle is now lifted from you. Go in peace, my son.

replies(2): >>43690359 #>>43691397 #
pjmlp ◴[15 Apr 25 11:42 UTC] No.43691397[source]▶
Just like we know how to make C safe (in theory), and many other cases in the industry.

The problem is that solutions don't exist, rather the lack of safety culture that keeps ignoring best practices unless they are imposed by regulations.

replies(1): >>43692436 #
1. chrisweekly ◴[15 Apr 25 13:31 UTC] No.43692436[source]▶
"problem is that solutions don't exist"

you meant "problem ISN'T that solutions...", right?

replies(1): >>43692807 #
2. pjmlp ◴[15 Apr 25 14:01 UTC] No.43692807[source]▶
Correct, typo. Thanks.