Open-Source MCP Security Gate Blocks Prompt Injections in Under 5ms
EstablishmentTough18 · reddit · 2026-10-13
A developer released agent-security-gate-x402 v1.9.0 on r/mcp, an open-source deterministic security gateway for the MCP ecosystem claiming to intercept common attacks in <5ms with zero extra LLM latency:
- Context: hooking Claude Desktop/Cursor to local MCP tools (filesystem, bash, DB) exposes attack vectors — indirect prompt injections can hijack tool arguments, and agents can be tricked into rm -rf, reading .env/SSH keys, or exfiltrating secrets. An LLM judge in the middle adds 500ms–1.5s.
- Shell guard: static inspection <2ms, catching reverse shells (/dev/tcp, netcat), destructive disk commands, piped obfuscation (base64 -d | sh), and credential harvesting.
- AST inspector: walks Python ASTs in <3ms, flagging os.system, subprocess.Popen, eval(), unauthorized sockets.
- Injection radar: multi-layer pattern scanning for DAN prompts and markdown image payload exfiltration.
- NLI fact checker: verifies numerical consistency against reference context.
- Also includes EIP-712 attestations and on-chain settlement across Solana/Polygon/Base/Arbitrum.
- One-line setup via uvx or pip in the Claude Desktop config.
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