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.

Is your site exposed to CVE-2026-63118?

Run a free security scan — no signup, results in seconds.

Weakness Type (CWE)

CWE-346 CWE-346

CWE-350 CWE-350

References

Other References

https://github.com/modelcontextprotocol/ruby-sdk/commit/ba543083a7594e7892b29464b89091816446ff7a https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0 https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-rcgv-9m7m https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-rcgv-9m7m

Frequently Asked Questions

What is CVE-2026-63118? +

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.

How do I check if I'm vulnerable to CVE-2026-63118? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-22077

OPPO Wallet APP contains a trusted domain validation flaw that allows attackers to bypass protected interface access restrictions, which may …

CVE-2026-45173

Idira Identity Browser Extension (Chrome, Firefox, and Edge builds) versions prior to 26.8.1 exhibit an origin validation flaw within its …

CVE-2025-3651

Improper Verification of Source of a Communication Channel in Work Desktop for Mac versions 10.8.1.46 and earlier allows attackers to …

CVE-2025-3462

"This issue is limited to motherboards and does not affect laptops, desktop computers, or other endpoints." An insufficient validation in …

CVE-2025-53399

In Sipwise rtpengine before 13.4.1.1, an origin-validation error in the endpoint-learning logic of the media-relay core allows remote attackers to …

CVE-2025-10193

DNS rebinding vulnerability in Neo4j Cypher MCP server allows malicious websites to bypass Same-Origin Policy protections and execute unauthorised tool …