medium6.9
CVE-2026-63118
MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients.
Impact
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 | Fixed in |
|---|---|---|---|
| rubygems | mcp | <= 0.22.0 | 0.23.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-rjr6-rcgv-9m7m
- https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-rcgv-9m7m
- https://nvd.nist.gov/vuln/detail/CVE-2026-63118
- https://github.com/modelcontextprotocol/ruby-sdk/commit/ba543083a7594e7892b29464b89091816446ff7a
- https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0