CVE-2026-63119 — MCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)
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 …
Published: 2026-07-29 · CVSS: 6.2 · CVSS 3.1
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7