AIKIDO-2026-705470

mcp is vulnerable to Denial of Service (DoS)

Denial of Service (DoS)GHSA-fmmv-w9g8-j3gc Published Oct 7, 2026

High Risk

This Affects:

mcp

0.0.1 - 1.29.0

Fixed in 1.29.1

2.0.0 - 2.0.1

Fixed in 2.1.0

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TL;DR

The SSE message endpoint and the OAuth authorization, token, registration, and revocation routes read the entire HTTP request body into memory before checking its size. A client that sends a very large request can grow process memory to two to three times the body size and exhaust it, taking the server offline. No credentials are required for the OAuth routes or for the SSE endpoint on a server that does not authenticate clients. The fix applies the existing request body size limit middleware to these endpoints and rejects oversized bodies with HTTP 413 before any parsing.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range and you run an MCP server over HTTP using the SSE transport or the OAuth authorization server routes without a reverse proxy that already caps request body size.