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OpenAdvisories
High · 7.5 CVE-2026-67432 EUVD-2026-50502GHSA-h669-8m4g-r2hc

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

Published Jul 29, 2026 · Updated Jul 29, 2026 · Assigned by GitHub_M

Description

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

VendorProductAffectedFixed
modelcontextprotocol ruby-sdk < 0.23.0 —

Affected packages

EcosystemPackageAffectedFixedRecord
RubyGems mcp < 0.23.0 0.23.0 GHSA-h669-8m4g-r2hc

References