Packages

HighVulnerabilityGHSA-f897-62hf-6gxqPublished 27 Oct 2026

MCP TypeScript SDK: HTTP server transports and handlers did not limit request body size or JSON-RPC batch length

Your version of @modelcontextprotocol/hono

Affected releases · @modelcontextprotocol/hono

  • 2.x2.0.0Fixed in 2.0.1

On 2.x, the newest line:

npm install @modelcontextprotocol/hono@2.0.1
Every release on a timeline

  1. Affected

    2.0.0

    1 release

  2. Fixed

    2.0.1 – 2.0.2

    2 releases, latest

3 stable releases of @modelcontextprotocol/hono, oldest to newest.
Your version of @modelcontextprotocol/node

Affected releases · @modelcontextprotocol/node

  • 2.x2.0.0Fixed in 2.1.0

On 2.x, the newest line:

npm install @modelcontextprotocol/node@2.1.0
Every release on a timeline

  1. Affected

    2.0.0

    1 release

  2. Fixed

    2.1.0 – 2.1.2

    3 releases, latest

4 stable releases of @modelcontextprotocol/node, oldest to newest.

What happens

Summary

In affected versions, MCP servers reachable over HTTP put no limit on the size of a POST body or on the number of messages in a JSON-RPC batch. Large requests could exhaust the server's memory, and one long batch could block it from serving anyone else. No credentials were needed, unless your application authenticates requests before they reach the SDK.

Am I affected?

Yes, if clients you do not fully trust can reach your server over Streamable HTTP. A body parser such as express.json() does not protect you, because it does not limit batch length. Servers that only use stdio are not affected.

Affected versions:

Fix

Upgrade to:

Bodies over 4 MiB now get 413, and batches over 100 messages get 400. If your clients send larger bodies, raise the new maxRequestBodySize option.

If you cannot upgrade yet, cap request body size in a reverse proxy.