Flowise before 3.1.3 validates Custom MCP stdio environment variables against a denylist using a case-sensitive comparison, so on Windows, where environment names are case-insensitive, supplying 'node_options' bypasses the NODE_OPTIONS denylist entry. An authenticated user who can configure a Custom MCP node can thereby inject NODE_OPTIONS --require and execute arbitrary code in the Flowise server context.
Flowise contains a path traversal vulnerability in the /api/v1/document-store/loader/process endpoint that allows unauthenticated attackers to write arbitrary files to the filesystem. Attackers can exploit unsanitized fileName parameters with ../ sequences to overwrite critical files like package.json and achieve remote code execution when the application restarts.