Bug 2535857

Summary: CVE-2026-64684 goose: RMCP: Sensitive HTTP headers leaked during cross-origin redirects [fedora-all]
Product: [Fedora] Fedora Reporter: Vladimir Vasilev <vvasilev>
Component: gooseAssignee: RHEL Lightspeed Maint <rhel-lightspeed>
Status: CLOSED CURRENTRELEASE QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: rawhideCC: jkonecny, rhel-lightspeed, rodolfo.olivieri3, rust-sig
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["25847dd5-a571-4d1c-adcb-141a7f08691b"]}
Fixed In Version: Doc Type: ---
Doc Text:
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Clone Of: Environment:
Last Closed: 2026-10-15 09:31:12 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On:    
Bug Blocks: 2535732    

Description Vladimir Vasilev 2026-09-17 08:36:23 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

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.
Comment 1 Jiri Konecny 2026-10-15 09:31:12 UTC 
Fixed by latest 1.45 Goose update.