fix(fetch): handle malformed input without crashing#3515
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anshul-garg27 wants to merge 1 commit intomodelcontextprotocol:mainfrom
Open
fix(fetch): handle malformed input without crashing#3515anshul-garg27 wants to merge 1 commit intomodelcontextprotocol:mainfrom
anshul-garg27 wants to merge 1 commit intomodelcontextprotocol:mainfrom
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mcp-server-fetch crashes on any malformed JSON-RPC input because server.run() is called with raise_exceptions=True. A single invalid byte on stdin terminates the server process via unhandled ExceptionGroup. Change to raise_exceptions=False to match the behavior of other reference servers (e.g., mcp-server-time, mcp-server-sqlite) which handle parse errors gracefully and continue serving. Fuzz testing showed fetch crashed on 61/65 test cases while other servers using raise_exceptions=False survived all 65. Fixes modelcontextprotocol#3359
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Summary
Change
raise_exceptions=Truetoraise_exceptions=Falseinmcp-server-fetch/server.pyto prevent the server from crashing on malformed JSON-RPC input.Fixes #3359
Problem
mcp-server-fetchterminates on any malformed JSON-RPC message becauseserver.run()is called withraise_exceptions=True(line 288). A single invalid byte on stdin kills the server process via unhandledExceptionGroup.Fuzz testing from the issue showed:
raise_exceptions=True)raise_exceptions=False)Fix
One-line change:
raise_exceptions=True→raise_exceptions=False, consistent with all other reference servers exceptgit(which also has this issue).Test plan
echo "NOT VALID JSON" | mcp-server-fetchshould no longer crash