CVE-2026-54309 is a critical flaw (CVSS 10.0) in n8n. When @n8n/mcp-browser runs with the HTTP transport, its MCP endpoint needs no authentication, so any client or visited website could drive browser tools. It is fixed in n8n 2.25.7 and 2.26.2. The default stdio transport is not affected.
What's affected
- n8n before 2.25.7 and before 2.26.2, per the record.
- Fixed in 2.25.7 and 2.26.2.
- Only setups that run @n8n/mcp-browser with the HTTP transport (the HTTP transport option). The advisory says the default stdio transport is not affected.
How to check if you're exposed
Look at how @n8n/mcp-browser is started on your machines. Search service files, scripts and shell history for the transport flag.
ps aux | grep -i mcp-browser
ss -ltnp | grep -i node
If it was started with the HTTP transport, note which interface and port it listens on. Also check whether the n8n AI Browser Bridge extension is installed and connected, because the advisory ties the browser control impact to that case.
What to do now
- Upgrade to n8n 2.25.7, 2.26.2 or later.
- Switch to the default stdio transport if you do not need HTTP.
- If HTTP is required, restrict the listening port to trusted clients with host firewall rules, as the advisory suggests.
- Disconnect the browser bridge when it is not in use.
- Consider whether the browser profile attached to the bridge holds sessions you would not want exposed.
Why it matters
The class is CWE-306, missing authentication for a critical function. An endpoint that can steer a real browser must prove who is calling. Here it did not, and the advisory notes that even a website the user visits could reach the endpoint.
The browser bridge makes this serious. The advisory lists navigation, JavaScript evaluation, and cookie and storage access against the real profile. The record does not mark the CVE as exploited in the wild. The first protection is to avoid exposing local tool servers over HTTP unless you have to.
For your own projects, the free in-browser dependency scan needs no install, and the Gold directory tracks this CVE.
Quick check
Is the stdio setup safe?
The advisory says the default stdio transport is not affected. The issue concerns the HTTP transport only.
Sources
Last reviewed: 19 October 2026.
