CVE-2026-63118

Summary

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.

Affected Software

VendorProductVersion RangeStatus
modelcontextprotocolruby-sdk< 0.23.0affected

Weaknesses

  • CWE-346: CWE-346: Origin Validation Error
  • CWE-350: CWE-350: Reliance on Reverse DNS Resolution for a Security-Critical Action

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: no
    • Technical Impact: partial

Additional References

References