[Django]-Django ERROR (EXTERNAL IP): Invalid HTTP_HOST header: '*.domain.com'

ISSUE: gunicorn (your Django App server) is getting an invalid host name.

when a request is made to the server (NginX) and the HTTP Host (or
user agent) is empty, nginx sets the HTTP host to the gunicorn sock.

Solution: Add/update a directive in your nginx conf (nginx.conf or sites-enabled/<your-site>.conf) from:

proxy_set_header Host $http_host;

to (if you don’t have it set, just add the following),

proxy_set_header Host $host;

Can put it inside the location, above the proxy_pass directive:

server {
    listen 8000;
    server_name 0.0.0.0;

    location / {
            proxy_set_header Host $host;
            include proxy_params;
            proxy_pass http://unix:/<your-path>/yourproject.sock;  

    }
}

The client that is making a request to your server has sent the following HTTP Host header:

Host: *.domain.com

This is invalid as per the HTTP specification – * is not allowed in the header – hence Django responds with a HTTP 400 response and logs the error.

This is not related to what you put in your ALLOWED_HOSTS setting, where * is permitted and tells Django to accept requests for any (valid) hostname (it will still reject invalid hostnames like *.domain.com).

As others have pointed out in the comments however, you should really configure nginx only to accept connections for specific hosts (server_name) so that such requests don’t even reach Django.

The problem for me causing this error was giving a non-standard domain name. (According to RFC 1034/1035).
My domain had an underscore in it (like "example_domain.com").

I removed the _ and it worked!

Instead of having following in settings.py,
ALLOWED_HOSTS = ['*']
(Not a good practice in production)

Follow this –
To respond to ‘example.com’ and any subdomains, start the domain with a dot
ALLOWED_HOSTS = ['.example.com', '203.0.113.5']