How to Change the Security Level in ComfyUI
ComfyUI is a powerful node-based interface for running Stable Diffusion models locally. Because it's designed to be flexible and hackable, it ships with configurable security settings — particularly around how it handles external connections, custom nodes, and API access. Knowing how to adjust these settings matters whether you're running ComfyUI strictly on your own machine or exposing it across a network.
What "Security Level" Means in ComfyUI
ComfyUI doesn't use a single toggle labeled "security level" the way a consumer firewall might. Instead, its security posture is controlled through a combination of launch arguments, configuration flags, and network exposure settings that together determine what the interface can do and who can reach it.
The most significant security-related controls involve:
--listen— whether ComfyUI binds to localhost only or to an external network interface--port— which port the server runs on--disable-auto-launch— whether a browser opens automatically on startup--enable-cors-header— whether cross-origin requests are accepted--preview-method— controls how image previews are generated, with minor performance and exposure implications- Custom node permissions — whether untrusted custom nodes can execute arbitrary code
These arguments are passed when launching ComfyUI, typically via the command line or a launch script.
How to Modify Launch Arguments
Most ComfyUI installations are started with a Python command or a shell/batch script. The security-relevant flags are appended to that command.
On Windows, you typically edit run_nvidia_gpu.bat or a similar .bat file in your ComfyUI folder. It will contain a line like:
python main.py You modify this to include flags:
python main.py --listen 127.0.0.1 --port 8188 On Linux/macOS, the equivalent is usually a .sh script or a direct terminal command:
python main.py --listen 127.0.0.1 --port 8188 If you're using a packaged distribution (like the portable Windows version), there may be a dedicated launcher file you can open in a text editor.
Key Security Flags and What They Do
| Flag | Default Behavior | Tightened Behavior |
|---|---|---|
--listen | Binds to 0.0.0.0 (all interfaces) in some builds | Set to 127.0.0.1 to restrict to localhost only |
--enable-cors-header | Disabled by default | Enabling opens cross-origin access — avoid unless needed |
--port | 8188 | Change to reduce exposure from port scanners |
--disable-auto-launch | Browser opens on start | Suppresses automatic browser launch |
🔒 The single most impactful setting for most users: whether --listen is set to 127.0.0.1 (local only) or 0.0.0.0 (accessible to any device on your network). If you're running ComfyUI on a home machine purely for personal use, binding to localhost prevents any other device from reaching the interface.
Custom Nodes and Code Execution Risk
One area where security becomes more nuanced is custom node installation. ComfyUI's ecosystem includes hundreds of community-built nodes, typically installed via ComfyUI Manager or by dropping folders into the custom_nodes directory.
Custom nodes run as Python code with the same privileges as the ComfyUI process itself. There is no sandbox. This means:
- A malicious or poorly written custom node can read files, make network requests, or execute system commands
- Installing nodes from unverified sources carries real risk
- Reviewing node source code (or relying on well-maintained, widely-used nodes) is the practical mitigation
ComfyUI Manager includes a security gate setting that controls whether it will install nodes flagged as potentially unsafe. This is found within the Manager's own settings panel, accessible from the ComfyUI interface under the Manager menu. Options typically range from allowing all installs to blocking anything not from a curated list.
API Access and the --api Consideration
ComfyUI exposes a local HTTP API by default. Any application or script that can reach the port can submit workflows and trigger generation. If you're running ComfyUI on a shared machine or in a cloud environment, this is a meaningful attack surface.
There is no built-in authentication layer in base ComfyUI. Access control relies entirely on network-level restrictions — meaning if the port is reachable, it's usable. For anything beyond a strictly local setup, putting ComfyUI behind a reverse proxy with authentication (like Nginx with basic auth) is the standard approach.
Variables That Determine the Right Configuration
How you should configure these settings depends on factors specific to your situation:
- Where ComfyUI is running — local desktop, home server, cloud VM, or shared workstation each carry different exposure profiles
- Who else is on your network — a home LAN is very different from a university network or workplace environment
- Whether you're using the API programmatically — automation workflows may require open access that solo local use doesn't
- Your custom node sources — heavy use of community nodes introduces different risk than running stock ComfyUI
- Your OS and firewall configuration — Windows Firewall, UFW, or cloud security groups may already be controlling port access independently
⚙️ A developer testing workflows on a private laptop has almost nothing to configure. Someone running ComfyUI as a shared service on a home server, or deploying it on a VPS, faces a genuinely different set of decisions about network binding, authentication, and node trust.
The technical controls exist and are straightforward to apply — but which combination makes sense depends entirely on your environment and what you're trying to protect against.