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[Security] Harden CLI dev command against injection on Windows #1904

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[Security] Harden CLI dev command against injection on Windows #1904

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10 changes: 9 additions & 1 deletion src/mcp/cli/cli.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
import importlib.metadata
import importlib.util
import os
import shlex
import subprocess
import sys
from pathlib import Path
Expand Down Expand Up @@ -275,8 +276,15 @@ def dev(

# Run the MCP Inspector command with shell=True on Windows
shell = sys.platform == "win32"
cmd_args = [npx_cmd, "@modelcontextprotocol/inspector"] + uv_cmd

if shell:
# On Windows with shell=True, I need to quote arguments to prevent injection
# and join them into a single string, as passing a list with shell=True is unsafe/undefined behavior
cmd_args = " ".join(shlex.quote(arg) for arg in cmd_args)

process = subprocess.run(
[npx_cmd, "@modelcontextprotocol/inspector"] + uv_cmd,
cmd_args,
check=True,
shell=shell,
env=dict(os.environ.items()), # Convert to list of tuples for env update
Expand Down