Open-Source Local Firewall for MCP
Simple-Factor-2165 · reddit · 2026-07-14
A developer has created MCP-Shield, an open-source local firewall designed to protect AI agents' MCP tool calls.
The core pain point: once an agent gets shell or tool permissions, it can be tricked by a single prompt injection into executing unintended actions. Existing permission systems often rely on the client, so the author chose to build a local proxy one layer below the MCP transport layer.
Design goals:
- Automatically allow obviously safe tool calls;
- Block obviously dangerous commands;
- Pause suspicious operations, executing them only after the user confirms, modifies, or rejects them.
The author explicitly states this doesn't "solve" prompt injection; if an attacker operates entirely within tools you already trust, the proxy can only do so much. However, it provides a unified layer of protection for clients like Claude Desktop, Claude Code, Cursor, VS Code, Windsurf, and Codex CLI.
Project commitments:
- 100% local execution;
- No cloud services, no accounts, no telemetry;
- MIT open-source license;
- Approval interface is a local web UI.
More from coding & agent
- Is inference latency becoming the biggest bottleneck for production AI agents? — Euphoric_Sea632 · 2026-09-11
- Anthropic researcher: 99% of engineers now run swarms of 300+ self-improving agents — AlishaOutridge · 2026-09-11
- Gergely Orosz: Shipping 10x PRs With AI Agents, Sites Fill With Small Regressions — ducha_aiki · 2026-09-11
- Same Echo Maze prompt, three frontier models: all passed visually but shipped the same hidden bug — eyishazyer · 2026-09-11
- Astra storyboards plus Minimax H3 per-shot generation boost video success rates — Hailuo_AI · 2026-09-11
- Codex tip: use Sol with Astra and Luna sub-agents to save usage — pvncher · 2026-09-11