MCP TypeScript server SDK: Shared transport or server instances delivered one HTTP client's messages to another

影響: npm:@modelcontextprotocol/server >= 2.0.0, < 2.3.0 → 2.3.0

In affected versions, an MCP server reached over HTTP could deliver one client's responses and notifications to another client. This happened when clients shared one stateless transport, or one McpServer or Server instance. Messages were matched to a connection by JSON-RPC id alone. SDK clients number requests from 0, so ids collide in normal use. Am I affected? Yes, if more than one client can reach your HTTP endpoint and your code creates the transport or the server once at startup, i…

Read on GitHub Advisory Database

On 10/21/2026, 05:07 AM, GitHub Advisory Database published "MCP TypeScript server SDK: Shared transport or server instances delivered one HTTP client's messages to another" (type: Advisory). Severity is "High" (high). Related technologies: JavaScript / Node.js. CVE: CVE-2026-111770.