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 validate the HTTP Host or Origin request headers, which allows a malicious browser page to use DNS rebinding to reach a locally running MCP server and invoke exposed tools. This issue is fixed in version 0.23.0.
Related Weaknesses (CWE)
References
- https://github.com/modelcontextprotocol/ruby-sdk/commit/ba543083a7594e7892b29464
- https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0
- https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-r
- https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-r
FAQ
What is CVE-2026-63118?
CVE-2026-63118 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 validate the HTTP Host o...
How severe is CVE-2026-63118?
CVSS scoring is not yet available for CVE-2026-63118. Check NVD for updates.
Is there a patch for CVE-2026-63118?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.