Vulnerability in Modelcontextprotocol Ruby-Sdk
CVE-2026-67431
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.
EPSS: 0.003 (21.6th percentile) — read the EPSS interpretation.
Affected products
- Modelcontextprotocol Ruby-sdk — versions < 0.23.0
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)