CVE-2026-67432

HIGH7.5

MCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport

Published Jul 29, 2026

Modified 3 weeks ago

Details

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem reads and parses an entire JSON-RPC POST body without a size limit, allowing an unauthenticated remote attacker to exhaust process memory. This issue is fixed in version 0.23.0.

References

WEB

https://github.com/modelcontextprotocol/ruby-sdk/commit/772e0cb1f9db69312006926eee59a7287ad50166

WEB

https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0

WEB

https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-h669-8m4g-r2hc

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2026-67432

CVSS Analysis

CVSS v3.1

7.5