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.
Scoring
- Severity
- MEDIUM
- CVSS base score
- 6.9
- CVSS vector
- CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
- EPSS probability
- 0.19%
- CWE
- CWE-346, CWE-350
- Published
- 2026-07-29
- Last modified
- 2026-07-29
Affected products
- modelcontextprotocol ruby-sdk
Weakness type
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