> in pure Bash.

Not really in "pure bash". Also this needs to be labeled as a "toy".

Using an external tool like 'jq' especially written in C for parsing JSON, one can craft a exploitable JSON input to achieve code execution on the MCP server.

What could possibly go wrong? Maybe this CVE-2025-48060 [0] [1]?

[0] https://github.com/jqlang/jq/issues/3327

[1] https://nvd.nist.gov/vuln/detail/CVE-2025-48060