Isolate MCP fetch tools from internal networks
mcp-server-fetch SSRF reached internal and cloud-metadata URLs · Security incident · X · @justelite · Oct 2026
A CVE describes the reference fetch MCP server fetching internal network and cloud metadata addresses. A public exploit exists; the poster says the fix was still awaiting merge.
Lesson
Run fetch-style MCP tools in a sandbox with no access to private networks or metadata endpoints.
Fix prompt
Copy this into your own AI tool (Cursor, Lovable, Claude Code, Bolt…). It's general guidance written by us. Review what the AI suggests before applying it.
I use MCP, which can read web pages, files, emails or tool output. Help me reduce the risk of prompt injection (hidden instructions in content the AI reads). 1) List what my setup can access (files, terminal, browser, MCP servers, email, databases) and what it can do without asking me. 2) Point out the riskiest combinations, e.g. reading untrusted content while also having access to secrets or the ability to send data out. 3) Suggest concrete settings: require approval for commands and network calls, remove MCP servers I don't need, use read-only tokens, and keep the tool updated. 4) Give me a short checklist to follow before opening untrusted repos or documents. Don't change anything until I've approved your plan. Never ask me to paste API keys, passwords or .env contents; tell me where to check them myself.
Source: X ↗