CVE-2026-54309: n8n: MCP Browser HTTP Transport Exposes Unauthenticated Browser-Control Sessions

When @n8n/mcp-browser is run in HTTP transport mode, the MCP endpoint accepts session initialization and tool invocation requests without any authentication. Any network-reachable client, or any website visited by the user, can establish an MCP session and invoke browser-control tools.

Where the n8n AI Browser Bridge extension is installed and a browser connection is active, an unauthenticated caller can access browser-control capabilities including navigation, JavaScript evaluation, and cookie and storage access against the user’s real browser profile.

This issue only affects instances where @n8n/mcp-browser is run with the HTTP transport (--transport http). The default transport is stdio, which is not affected.