CVE-2026-63118

MCP Ruby SDK: Streamable HTTP transport lacks DNS-rebinding (Host/Origin) protection

Published: Jul 29, 2026Updated: Jul 30, 2026 Sources: CVE List NVDCWE-346

N/ACVSS

NVD MITRE

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.

No summary for this CVE yet.

Weaknesses

CWE-346 CWE-350

Affected Products

modelcontextprotocol

oss-projectaka mcp, model context protocol

ruby-sdkMixed

AI / ML / ai-agent-tooling

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

References

https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-rcgv-9m7m

github.com

https://github.com/modelcontextprotocol/ruby-sdk/commit/ba543083a7594e7892b29464b89091816446ff7a

github.com

https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0

github.com

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