CVE-2026-67431 — MCP Ruby SDK: Ruby SSE Session Poisoning
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 b…
Published: 2026-07-29 · CVSS: 8.3 · CVSS 4.0
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 bind a session ID to a session owner, allowing an attacker with a stolen session ID to send tools/call requests that execute in the victim's session. This issue is fixed in version 0.23.0.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7