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OpenAdvisories
Medium · 5.3 CVE-2026-67430 EUVD-2026-50498GHSA-52jp-gj8w-j6xh

MCP Ruby SDK: Unbounded session retention in StreamableHTTPTransport allows memory exhaustion via initialize flood

Published Jul 29, 2026 · Updated Jul 30, 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 does not expire sessions by default, so repeated initialize requests retain unbounded ServerSession objects and can 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-52jp-gj8w-j6xh

References