{"id":"CVE-2026-42559","summary":"RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport","details":"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.","aliases":["GHSA-89vp-x53w-74fx","GHSA-fvh2-gm75-j4j7","RUSTSEC-2026-0140","RUSTSEC-2026-0189"],"modified":"2026-08-12T03:51:30.436710277Z","published":"2026-05-14T14:24:56.090Z","related":["CGA-9xhh-g3m3-9725"],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-346","CWE-350"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42559.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42559.json"},{"type":"ADVISORY","url":"https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-89vp-x53w-74fx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-42559"},{"type":"REPORT","url":"https://github.com/modelcontextprotocol/rust-sdk/issues/815"},{"type":"REPORT","url":"https://github.com/modelcontextprotocol/rust-sdk/issues/822"},{"type":"FIX","url":"https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3"},{"type":"FIX","url":"https://github.com/modelcontextprotocol/rust-sdk/pull/764"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/modelcontextprotocol/rust-sdk","events":[{"introduced":"0"},{"fixed":"8e22aa2de28df5a285eed87c11cd89bf15fa90d3"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"1.4.0"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["rmcp-v1.3.0","rmcp-macros-v1.3.0","rmcp-v1.2.0","rmcp-macros-v1.2.0","rmcp-v1.1.1","rmcp-macros-v1.1.1","rmcp-v1.1.0","rmcp-macros-v1.1.0","rmcp-v1.0.0","rmcp-macros-v1.0.0","rmcp-v1.0.0-alpha","rmcp-macros-v1.0.0-alpha","rmcp-v0.17.0","rmcp-macros-v0.17.0","rmcp-v0.16.0","rmcp-macros-v0.16.0","rmcp-v0.15.0","rmcp-macros-v0.15.0","rmcp-v0.14.0","rmcp-macros-v0.14.0","rmcp-v0.13.0","rmcp-macros-v0.13.0","rmcp-v0.12.0","rmcp-macros-v0.12.0","rmcp-v0.11.0","rmcp-macros-v0.11.0","rmcp-v0.10.0","rmcp-macros-v0.10.0","rmcp-v0.9.1","rmcp-macros-v0.9.1","rmcp-v0.9.0","rmcp-macros-v0.9.0","rmcp-v0.8.5","rmcp-macros-v0.8.5","rmcp-v0.8.4","rmcp-macros-v0.8.4","rmcp-v0.8.3","rmcp-macros-v0.8.3","rmcp-v0.8.2","rmcp-macros-v0.8.2","rmcp-v0.8.1","rmcp-macros-v0.8.1","rmcp-v0.8.0","rmcp-macros-v0.8.0","rmcp-v0.7.0","rmcp-macros-v0.7.0","rmcp-v0.6.3","rmcp-macros-v0.6.3","rmcp-v0.6.2","rmcp-macros-v0.6.2","rmcp-v0.6.1","rmcp-macros-v0.6.1","rmcp-v0.6.0","rmcp-macros-v0.6.0","rmcp-v0.5.0","rmcp-macros-v0.5.0","rmcp-v0.4.1","rmcp-macros-v0.4.1","rmcp-v0.4.0","rmcp-macros-v0.4.0","rmcp-v0.3.2","rmcp-macros-v0.3.2","rmcp-v0.3.1","rmcp-macros-v0.3.1","rmcp-v0.3.0","rmcp-macros-v0.3.0","rmcp-v0.2.1","rmcp-macros-v0.2.1","rmcp-v0.2.0","rmcp-macros-v0.2.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-42559.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"}]}