Change default binding from 0.0.0.0 to 127.0.0.1 to align with security recommendations #738
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> When running locally, servers SHOULD bind only to localhost (127.0.0.1) rather than all network interfaces (0.0.0.0)
> When running locally, servers SHOULD bind only to localhost (127.0.0.1) rather than all network interfaces (0.0.0.0)
> When running locally, servers SHOULD bind only to localhost (127.0.0.1) rather than all network interfaces (0.0.0.0)
> When running locally, servers SHOULD bind only to localhost (127.0.0.1) rather than all network interfaces (0.0.0.0)
> When running locally, servers SHOULD bind only to localhost (127.0.0.1) rather than all network interfaces (0.0.0.0)
> When running locally, servers SHOULD bind only to localhost (127.0.0.1) rather than all network interfaces (0.0.0.0)
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Change default server settings and all example code to bind to
127.0.0.1rather than0.0.0.0Motivation and Context
The official docs note that
This change attempts to make that behavior the default and reduce the chances of successful DNS rebinding attacks.
How Has This Been Tested?
Not tested.
Breaking Changes
This could be breaking in the scenario where users are relying on this default behavior to make the server accessible outside of localhost. An alternative would be to remove the change to src/mcp/server/fastmcp/server.py but keep the changes in example files and comments. That version would not be breaking.
Types of changes
Checklist
Additional context