CVE-2026-63119

Medium

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.

SeverityMedium

CVSS6.2

Exploit probability—

ProductModelcontextprotocol Ruby-sdk

PublishedJul 29, 2026

First seenJul 29, 2026

Weakness typeCWE-400Uncontrolled resource consumption CWE-770Allocation of resources without limits

How to fix

Sources list no fixed version or patch link for this vulnerability.

Affected products

Product	Affected versions	Fixed in
modelcontextprotocol ruby-sdk	< 0.23.0	—

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