CVE-2026-54309: n8n: 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.
Other sources
n8n is an open source workflow automation platform. Prior to 2.25.7 and 2.26.2, 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). This vulnerability is fixed in 2.25.7 and 2.26.2.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/n8nto a version that resolves this vulnerability.Fixed in 2.25.7 - Upgrade
Upgrade
npm/n8nto a version that resolves this vulnerability.Fixed in 2.26.2 - Upgrade
Upgrade
n8nto a version that resolves this vulnerability.Fixed in 2.25.7 - Upgrade
Upgrade
n8nto a version that resolves this vulnerability.Fixed in 2.26.2 - Configuration
When configuring @n8n/mcp-browser, avoid running it with HTTP transport (--transport http); use the default stdio transport instead.
@n8n/mcp-browser transport = stdio - Compensating control
If HTTP transport is required for @n8n/mcp-browser (--transport http), restrict network access to the listening port to trusted clients only using host-based firewall rules.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-54309?
The severity of CVE-2026-54309 is rated as critical with a score of 10.
How do I fix CVE-2026-54309?
To fix CVE-2026-54309, immediately apply authentication mechanisms to the MCP endpoint when running in HTTP transport mode.
What type of vulnerability is CVE-2026-54309?
CVE-2026-54309 is an authentication bypass vulnerability that allows unauthorized session initialization and tool invocation.
What is the impact of CVE-2026-54309?
The impact of CVE-2026-54309 allows any network-reachable client to establish an MCP session and invoke browser-control tools without authentication.
Which software is affected by CVE-2026-54309?
CVE-2026-54309 affects the npm package n8n when it is run in HTTP transport mode.