{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-64684", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-07-20T17:12:12.892Z", "datePublished": "2026-09-16T21:18:48.886Z", "dateUpdated": "2026-09-16T21:18:48.886Z"}, "containers": {"cna": {"title": "RMCP: Custom HTTP headers leak to cross-origin redirect targets", "problemTypes": [{"descriptions": [{"cweId": "CWE-200", "lang": "en", "description": "CWE-200: Exposure of Sensitive Information to an Unauthorized Actor", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 6.8, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N", "version": "3.1"}}], "references": [{"name": "https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-9g45-5xwm-f3wc", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-9g45-5xwm-f3wc"}, {"name": "https://github.com/modelcontextprotocol/rust-sdk/pull/936", "tags": ["x_refsource_MISC"], "url": "https://github.com/modelcontextprotocol/rust-sdk/pull/936"}, {"name": "https://github.com/modelcontextprotocol/rust-sdk/commit/496902b9cf2c8a947454718da31829ae776b969b", "tags": ["x_refsource_MISC"], "url": "https://github.com/modelcontextprotocol/rust-sdk/commit/496902b9cf2c8a947454718da31829ae776b969b"}, {"name": "https://github.com/modelcontextprotocol/rust-sdk/releases/tag/rmcp-v2.1.0", "tags": ["x_refsource_MISC"], "url": "https://github.com/modelcontextprotocol/rust-sdk/releases/tag/rmcp-v2.1.0"}], "affected": [{"vendor": "modelcontextprotocol", "product": "rust-sdk", "versions": [{"version": "< 2.1.0", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-09-16T21:18:48.886Z"}, "descriptions": [{"lang": "en", "value": "RMCP is an official Rust SDK for the Model Context Protocol. Prior to 2.1.0, the rmcp crate's StreamableHttpClientTransport in crates/rmcp/src/transport/common/reqwest/streamable_http_client.rs builds its default_http_client with reqwest's automatic redirect policy and applies caller-supplied values from StreamableHttpClientTransportConfig.custom_headers without marking them as sensitive. When a malicious or compromised MCP endpoint returns a cross-origin 307 or 308 redirect, reqwest follows the redirect and apply_custom_headers causes custom API keys or authentication tokens to be replayed to the new origin, where an attacker can capture and reuse them. The separate auth_header path is not affected because it uses the standard Authorization header, which reqwest strips on cross-origin redirects. This issue is fixed in version 2.1.0."}], "source": {"advisory": "GHSA-9g45-5xwm-f3wc", "discovery": "UNKNOWN"}}}}

{}

{"affected": [{"affectedData": [{"product": "rust-sdk", "vendor": "modelcontextprotocol", "versions": [{"status": "affected", "version": "< 2.1.0"}]}], "source": "security-advisories@github.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "RMCP is an official Rust SDK for the Model Context Protocol. Prior to 2.1.0, the rmcp crate's StreamableHttpClientTransport in crates/rmcp/src/transport/common/reqwest/streamable_http_client.rs builds its default_http_client with reqwest's automatic redirect policy and applies caller-supplied values from StreamableHttpClientTransportConfig.custom_headers without marking them as sensitive. When a malicious or compromised MCP endpoint returns a cross-origin 307 or 308 redirect, reqwest follows the redirect and apply_custom_headers causes custom API keys or authentication tokens to be replayed to the new origin, where an attacker can capture and reuse them. The separate auth_header path is not affected because it uses the standard Authorization header, which reqwest strips on cross-origin redirects. This issue is fixed in version 2.1.0."}], "id": "CVE-2026-64684", "lastModified": "2026-09-16T22:17:04.577", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 6.8, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 4.0, "source": "security-advisories@github.com", "type": "Secondary"}]}, "published": "2026-09-16T22:17:04.577", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/modelcontextprotocol/rust-sdk/commit/496902b9cf2c8a947454718da31829ae776b969b"}, {"source": "security-advisories@github.com", "url": "https://github.com/modelcontextprotocol/rust-sdk/pull/936"}, {"source": "security-advisories@github.com", "url": "https://github.com/modelcontextprotocol/rust-sdk/releases/tag/rmcp-v2.1.0"}, {"source": "security-advisories@github.com", "url": "https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-9g45-5xwm-f3wc"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-200"}], "source": "security-advisories@github.com", "type": "Primary"}]}

{}

{}