n8n before 1.123.67, 2.31.5, and 2.32.1 contains a prototype pollution vulnerability in the Edit Fields (Set) node. The node assigns output fields via a dot-notation path setter without restricting the field name, allowing an authenticated user to name a field after an inherited built-in method path and corrupt a shared global in the main Node.js process. Because that global is used on the request-authentication path, the instance then fails every authenticated request, causing an instance-wide denial of service for all users until the process is restarted.