AIKIDO-2026-725245
mcp is vulnerable to Uncontrolled Resource Consumption
75
High Risk
This Affects:
mcpTL;DR
The MCP::Server::Transports::StreamableHTTPTransport reads the entire HTTP request body into a Ruby string and parses it with JSON.parse before any session validation, with no size or Content-Length limit and no bound on JSON nesting. An unauthenticated remote client can send a single oversized JSON-RPC POST that inflates the worker's memory many times over. This causes memory-exhaustion denial of service and can OOM-kill the worker. The fix caps request body reads via max_request_bytes and limits JSON nesting, rejecting oversized requests.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and expose the Streamable HTTP transport to untrusted clients.
Background info
mcp is vulnerable to Uncontrolled Resource Consumption in versions 0.1.0 - 0.22.0.
How to fix this
Upgrade the mcp library to the patch version.
Links
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