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

OpenClaw CLI supports remote MCP Streamable HTTP servers with operator-configured custom headers. In affected versions (>=2026.1.29 <2026.5.12), these custom headers could be forwarded to another origin if the MCP endpoint responded with a cross-origin redirect. This behavior risks exposing sensitive headers like API keys or tenant-routing headers to the redirect target. The vulnerability is limited to configurations using 'transportType: "streamable-http"' with custom headers under 'mcp.servers.*.headers' and MCP endpoints capable of redirecting to other origins. The first stable patched version is 2026.5.12.

Sensitive custom headers configured for MCP Streamable HTTP servers, including API keys or tenant-routing headers, could be leaked to a redirect target if the MCP endpoint issues a cross-origin redirect. The scope of exposure depends on the specific headers configured by the operator. This could lead to unauthorized access or misuse of credentials associated with the MCP server.

Upgrade OpenClaw CLI to version 2026.5.12 or later to apply the official fix. Before upgrading, avoid using custom MCP headers with MCP servers that are not fully trusted. Additionally, rotate any MCP-specific credentials that may have been exposed due to this vulnerability.