Moderate severityNVD Advisory· Published Jul 29, 2026· Updated Jul 29, 2026
MCP Ruby SDK: Streamable HTTP transport lacks DNS-rebinding (Host/Origin) protection
CVE-2026-63118
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
mcpRubyGems | < 0.23.0 | 0.23.0 |
Affected products
2- Range: <0.23.0
Patches
Vulnerability mechanics
References
5- github.com/advisories/GHSA-rjr6-rcgv-9m7mghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-63118ghsaADVISORY
- github.com/modelcontextprotocol/ruby-sdk/commit/ba543083a7594e7892b29464b89091816446ff7aghsax_refsource_MISCWEB
- github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0ghsax_refsource_MISCWEB
- github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-rcgv-9m7mghsax_refsource_CONFIRMWEB
News mentions
0No linked articles in our index yet.