Unable to Use MCP Endpoint on Remote Deployments Due to DNS Rebinding Protection #7902
Description
Describe the bug
The introduction of DNS rebinding protections in FastMCP makes the MCP endpoint inaccessible in remote deployments.
Related discussion and potential fixes are tracked here:
modelcontextprotocol/python-sdk#1798
marimo/marimo/_mcp/server/main.py
Line 52 in d7421e1
Will you submit a PR?
- Yes
Environment
Details
{
"marimo": "0.19.4",
"editable": false,
"location": "/Users/kyrre.wahl.kongsgaard/projects/security-data-platform/apps/marimo/.venv/lib/python3.13/site-packages/marimo",
"OS": "Darwin",
"OS Version": "25.2.0",
"Processor": "arm",
"Python Version": "3.13.3",
"Locale": "en_US",
"Binaries": {
"Browser": "143.0.7499.193",
"Node": "v24.10.0"
},
"Dependencies": {
"click": "8.3.1",
"docutils": "0.22.4",
"itsdangerous": "2.2.0",
"jedi": "0.19.2",
"markdown": "3.10",
"narwhals": "2.15.0",
"packaging": "25.0",
"psutil": "7.2.1",
"pygments": "2.19.2",
"pymdown-extensions": "10.20",
"pyyaml": "6.0.3",
"starlette": "0.52.1",
"tomlkit": "0.14.0",
"typing-extensions": "4.15.0",
"uvicorn": "0.40.0",
"websockets": "15.0.1"
},
"Optional Dependencies": {
"altair": "6.0.0",
"anywidget": "0.9.21",
"duckdb": "1.4.3",
"ibis-framework": "11.0.0",
"loro": "1.10.3",
"mcp": "1.25.0",
"nbformat": "5.10.4",
"openai": "2.15.0",
"pandas": "2.3.3",
"polars": "1.37.1",
"pyarrow": "23.0.0",
"pytest": "9.0.2",
"python-lsp-ruff": "2.3.0",
"python-lsp-server": "1.14.0",
"ruff": "0.14.13",
"sqlglot": "28.6.0",
"watchdog": "6.0.0"
},
"Experimental Flags": {
"mcp_docs": true,
"external_agents": true,
"chat_sidebar": true,
"chat_modes": true
}
}```
</details>
### Code to reproduce
marimo deployed as an ECS task