CVE-2026-67432: Modelcontextprotocol Ruby-SDK

High severity, CVSS 7.5. EPSS: 0.8% chance of exploitation in the next 30 days.

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.

Affected products

• Modelcontextprotocol Ruby-SDK: before 0.23.0 (fixed in 0.23.0)

Published 2026-07-29. Last modified 2026-07-30.