MEDIUMCVSS 6.9EPSS 0.2%

CVE-2026-63118

CVE-2026-63118 updated by NVD

Published: 2026-07-30
Modified: 2026-07-31
EPSS percentile: 10%
Sources: github-advisory, nvd

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 packages

Ecosystem	Package	Affected versions	Fixed versions
RubyGems	mcp	—	0.23.0

Remediation: Upgrade to 0.23.0 or later.

References

https://nvd.nist.gov/vuln/detail/CVE-2026-63118

Includes data from the GitHub Advisory Database, licensed under CC-BY 4.0.

Includes data from the National Vulnerability Database (NIST). NVD data is in the public domain; this page is not endorsed by NIST.

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EPSS scores provided by the FIRST.org Exploit Prediction Scoring System.