CVE-2026-64684
- Source
- https://cve.org/CVERecord?id=CVE-2026-64684
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64684.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2026-64684
- Aliases
- Published
- 2026-09-16T21:18:48Z
- Modified
- 2026-09-18T03:48:29Z
- Severity
-
- 6.8 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N CVSS Calculator
- Summary
- RMCP: Custom HTTP headers leak to cross-origin redirect targets
- Details
-
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.
- Database specific
{ "cna_assigner": "GitHub_M", "cwe_ids": [ "CWE-200" ], "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64684.json" }- References
-
- https://github.com/modelcontextprotocol/rust-sdk/releases/tag/rmcp-v2.1.0
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64684.json
- https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-9g45-5xwm-f3wc
- https://nvd.nist.gov/vuln/detail/CVE-2026-64684
- https://github.com/modelcontextprotocol/rust-sdk/commit/496902b9cf2c8a947454718da31829ae776b969b
- https://github.com/modelcontextprotocol/rust-sdk/pull/936
Affected packages
Git / github.com/modelcontextprotocol/rust-sdk
Affected ranges
- Type
- GIT
- Repo
- https://github.com/modelcontextprotocol/rust-sdk
- Events
-
Introduced0 Unknown introduced commit / All previous commits are affectedFixedFixed
- Database specific
-
Show details
{ "extracted_events": [ { "introduced": "0" }, { "fixed": "2.1.0" } ], "source": [ "AFFECTED_FIELD", "REFERENCES" ] }