{"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"}]}

{"bugzilla": {"description": "rmcp: RMCP: Sensitive HTTP headers leaked during cross-origin redirects", "id": "2535732", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2535732"}, "csaw": false, "cvss3": {"cvss3_base_score": "6.8", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N", "status": "draft"}, "cwe": "CWE-212", "details": ["A flaw was found in the `rmcp` component. This vulnerability allows a remote attacker to disclose sensitive information. When the `rmcp` crate's HTTP client processes a redirect to a different web address (cross-origin redirect) from a malicious or compromised Model Context Protocol (MCP) endpoint, it can inadvertently replay custom HTTP headers, such as API keys or authentication tokens, to the new, untrusted destination. This enables an attacker to capture and potentially reuse these sensitive credentials."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}, "name": "CVE-2026-64684", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "goose", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "goose", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-09-16T21:18:48Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-64684\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-64684\nhttps://github.com/modelcontextprotocol/rust-sdk/commit/496902b9cf2c8a947454718da31829ae776b969b\nhttps://github.com/modelcontextprotocol/rust-sdk/pull/936\nhttps://github.com/modelcontextprotocol/rust-sdk/releases/tag/rmcp-v2.1.0\nhttps://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-9g45-5xwm-f3wc"], "threat_severity": "Moderate"}

{}