As it has been mentioned before, MCP isn't "vulnerable". It's just on the other side of your air lock. Think of your MCP as a different client application. The whole thing is just a client. The fact that you need to write a client for your client is.... something, but your MCP app is a client app. It's boundaries with your service should be understood as such.
Saying MCP is vulnerable is like saying "Web applications are vulnerable. Anyone can see the API calls you're making and modify them or trick your UI app to make a different call and hack your system". Obviously that's mostly nonsense, but not 100% wrong either. You see it a lot with very very inexperienced developers who think "just because my App is Android/iOS only I don't need to worry about authn/authz". There was just a story on here few weeks ago about some New Zealand startup that did that
Saying MCP is vulnerable is like saying "Web applications are vulnerable. Anyone can see the API calls you're making and modify them or trick your UI app to make a different call and hack your system". Obviously that's mostly nonsense, but not 100% wrong either. You see it a lot with very very inexperienced developers who think "just because my App is Android/iOS only I don't need to worry about authn/authz". There was just a story on here few weeks ago about some New Zealand startup that did that