Vulnerability Description
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.
Related Weaknesses (CWE)
References
- https://github.com/modelcontextprotocol/ruby-sdk/commit/35466605319a34e4c7808712
- https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0
- https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-5p9g-j
- https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-5p9g-j
FAQ
What is CVE-2026-67431?
CVE-2026-67431 is a documented vulnerability. 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 s...
How severe is CVE-2026-67431?
CVSS scoring is not yet available for CVE-2026-67431. Check NVD for updates.
Is there a patch for CVE-2026-67431?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.