HIGH 7.7 GitHub
CVE-2026-111770
MCP TypeScript server SDK: Shared transport or server instances delivered one HTTP client's messages to another
### Summary
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 onc
Affected Products
- npm/@modelcontextprotocol/server >= 2.0.0, < 2.3.0
References
- https://github.com/advisories/GHSA-jm63-cq47-j5jp
- https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-jm63-cq47-
- https://github.com/modelcontextprotocol/typescript-sdk/pull/2918
- https://github.com/modelcontextprotocol/typescript-sdk/commit/84804c22e45a662675a198f853b7
This high severity vulnerability with a CVSS score of 7.7 was published on 2026-10-20 via GitHub. Affected: npm/@modelcontextprotocol/server >= 2.0.0, < 2.3.0.
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