As a response to ticket https://trac.nginx.org/nginx/ticket/1724, Nginx 1.17.9 and newer ( https://hg.nginx.org/nginx/rev/4f18393a1d51 ) no longer accept HTTP requests with more than one "Host" header due to an additional condition in ngx_http_process_host. That change "broke" my server, as that server is being accessed by an old piece of hardware that seems to have a similby Leseratte10 - Ideas and Feature Requests