{"id":"CVE-2026-42559","state":"PUBLISHED","title":"RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport","description":"RMCP is an official Rust SDK for the Model Context Protocol. Prior to version 1.4.0, the rmcp crate's Streamable HTTP server transport (crates/rmcp/src/transport/streamable_http_server/) did not validate the incoming Host header. This allowed a malicious public website, via a DNS rebinding attack, to send authenticated requests to an MCP server running on the victim's loopback or private-network interface. This vulnerability is fixed in 1.4.0.","publishedAt":"2026-05-14T14:24:56.090Z","updatedAt":"2026-05-14T16:00:33.149Z","severity":{"score":8.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["modelcontextprotocol rust-sdk"],"affected":[{"vendor":"modelcontextprotocol","product":"rust-sdk","versions":[{"version":"< 1.4.0","status":"affected"}]}],"references":["https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-89vp-x53w-74fx","https://github.com/modelcontextprotocol/rust-sdk/issues/815","https://github.com/modelcontextprotocol/rust-sdk/issues/822","https://github.com/modelcontextprotocol/rust-sdk/pull/764","https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3"],"weaknesses":["CWE-346","CWE-350"],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/42xxx/CVE-2026-42559.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-42559","state":"PUBLISHED","datePublished":"2026-05-14T14:24:56.090Z","dateUpdated":"2026-05-14T16:00:33.149Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-04-28T16:56:50.192Z"},"containers":{"cna":{"title":"RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport","descriptions":[{"lang":"en","value":"RMCP is an official Rust SDK for the Model Context Protocol. Prior to version 1.4.0, the rmcp crate's Streamable HTTP server transport (crates/rmcp/src/transport/streamable_http_server/) did not validate the incoming Host header. This allowed a malicious public website, via a DNS rebinding attack, to send authenticated requests to an MCP server running on the victim's loopback or private-network interface. This vulnerability is fixed in 1.4.0."}],"affected":[{"vendor":"modelcontextprotocol","product":"rust-sdk","versions":[{"version":"< 1.4.0","status":"affected"}]}],"references":[{"url":"https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-89vp-x53w-74fx","name":"https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-89vp-x53w-74fx","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/modelcontextprotocol/rust-sdk/issues/815","name":"https://github.com/modelcontextprotocol/rust-sdk/issues/815","tags":["x_refsource_MISC"]},{"url":"https://github.com/modelcontextprotocol/rust-sdk/issues/822","name":"https://github.com/modelcontextprotocol/rust-sdk/issues/822","tags":["x_refsource_MISC"]},{"url":"https://github.com/modelcontextprotocol/rust-sdk/pull/764","name":"https://github.com/modelcontextprotocol/rust-sdk/pull/764","tags":["x_refsource_MISC"]},{"url":"https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3","name":"https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":8.8,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-346","lang":"en","description":"CWE-346: Origin Validation Error","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-350","lang":"en","description":"CWE-350: Reliance on Reverse DNS Resolution for a Security-Critical Action","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-05-14T14:24:56.090Z"},"source":{"advisory":"GHSA-89vp-x53w-74fx","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-14T16:00:22.834947Z","id":"CVE-2026-42559","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-05-14T16:00:33.149Z"}}]}}}