{"id":"CVE-2026-63118","summary":"MCP Ruby SDK: Streamable HTTP transport lacks DNS-rebinding (Host/Origin) protection","details":"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.","aliases":["GHSA-rjr6-rcgv-9m7m"],"modified":"2026-08-12T03:51:34.998472600Z","published":"2026-07-29T19:07:33.452Z","database_specific":{"cwe_ids":["CWE-346","CWE-350"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63118.json","cna_assigner":"GitHub_M"},"references":[{"type":"WEB","url":"https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63118.json"},{"type":"ADVISORY","url":"https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-rcgv-9m7m"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63118"},{"type":"FIX","url":"https://github.com/modelcontextprotocol/ruby-sdk/commit/ba543083a7594e7892b29464b89091816446ff7a"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/modelcontextprotocol/ruby-sdk","events":[{"introduced":"0"},{"fixed":"ba543083a7594e7892b29464b89091816446ff7a"},{"fixed":"95feef2dcfba25d92a8963d14b7a3b279122f36f"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"0.23.0"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["v0.22.0","v0.21.0","v0.20.0","v0.19.0","v0.18.0","v0.17.0","v0.16.0","v0.15.0","v0.14.0","v0.13.0","v0.12.0","v0.11.0","v0.10.0","v0.9.2","v0.9.1","v0.8.0","v0.9.0","v0.7.1","v0.7.0","v0.6.0","v0.5.0","v0.4.0","v0.3.0","v0.2.0","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63118.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}