n8n: MCP Browser HTTP Transport Exposes Unauthenticated Browser-Control Sessions

## Impact 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. ## Patches The issue has been fixed in n8n versions 2.25.7, and 2.26.2. Users should upgrade to one of these versions or later to remediate the vulnerability. ## Workarounds If upgrading is not immediately possible, administrators should consider the following temporary mitigations: - Avoid running `@n8n/mcp-browser` with the HTTP transport; use the default stdio transport instead. - If HTTP transport is required, restrict network access to the listening port to trusted clients only using host-based firewall rules. These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.

CVSS 3.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L

Severity from

GitHub (reviewed advisory)

Weakness

CWE-306

Also known as

CVE-2026-54309

• github.com/n8n-io/n8n/security/advisories/GHSA-qrx8-25qr-5r7v
• nvd.nist.gov/vuln/detail/CVE-2026-54309
• github.com/n8n-io/n8n