CVE-2026-53840: OpenClaw: MCP Streamable HTTP redirects could forward configured custom headers to another origin

Summary

OpenClaw supports remote MCP Streamable HTTP servers with operator-configured custom headers. In affected releases, those headers could be forwarded when the MCP endpoint responded with a cross-origin redirect.

This issue is limited to configured MCP Streamable HTTP servers that use custom headers. It does not expose unrelated OpenClaw credentials.

Affected configurations

This affects deployments where an MCP server is configured with:

• transportType: "streamable-http"
• sensitive custom headers under mcp.servers.*.headers
• an MCP endpoint that is malicious, compromised, or able to redirect to another origin

Impact

Custom MCP headers, such as API keys or tenant-routing headers, could be sent to the redirect target. The exposed credential scope depends on the header the operator configured for that MCP server.

Patched Versions

The first stable patched version is 2026.5.12.

Mitigations

Upgrade to [email protected] or later. Before upgrading, avoid custom MCP headers with servers you do not fully trust, and rotate any MCP-specific credentials that may have been exposed by a redirecting endpoint.