Am I affected by MCP TypeScript server SDK sent one HTTP client's messages to another? What should I do?
An MCP server reached over HTTP could deliver one client's responses and notifications to another client.
Affected: @modelcontextprotocol/server 2.0.0 through 2.2.0. Fixed in: 2.3.0. What should you check, and what should you do about it?
Full incident page with sources: https://agentarmorhq.com/incidents/2026/10/cve-2026-111770-modelcontextprotocol-server-mcp-typescript-server-sdk (opens external site) Tool page: https://agentarmorhq.com/skills/server (opens external site)
1 answer
Am I affected? Affected: @modelcontextprotocol/server 2.0.0 through 2.2.0. Fixed in: 2.3.0.
- Check your version: run
npm ls @modelcontextprotocol/server. Versions >= 2.0.0, < 2.3.0 of @modelcontextprotocol/server are affected.
What to do now
- Upgrade to the fixed version: run
npm install @modelcontextprotocol/server@2.3.0(first patched version 2.3.0). - Upgrade to @modelcontextprotocol/server 2.3.0 or later.
- Pass a factory to createMcpHandler() that builds a new McpServer on every call.
- Or build a new McpServer and a new transport inside the request handler, once per request.
- Or set sessionIdGenerator and keep one McpServer and one transport per session.
General practice, not from the source: if the affected software could read tokens or credentials, rotate them after upgrading; pin versions and review changes before updating tools your agents run.
Sources
- GitHub Advisory Database: https://github.com/advisories/GHSA-jm63-cq47-j5jp (opens external site)
Full incident page: https://agentarmorhq.com/incidents/2026/10/cve-2026-111770-modelcontextprotocol-server-mcp-typescript-server-sdk (opens external site) Tool page: https://agentarmorhq.com/skills/server (opens external site)
Did this work for you?- Check your version: run