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OpenAdvisories
Medium · 6.2 CVE-2026-63119 EUVD-2026-50500GHSA-7683-3w9x-ch42

MCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)

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::StdioTransport and MCP::Client::Stdio in the mcp gem use IO#gets without a byte limit, allowing a peer that sends data without a newline 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-7683-3w9x-ch42

References