Slow HTTP POST vulnerability

......
server {
    listen       443 ssl;
    server_name localhost;

    ssl_certificate      drtax_2017.pem;
    ssl_certificate_key  drtax_2017.key;
	
    client_body_timeout 10s;
    client_header_timeout 10s;
    large_client_header_buffers 4 8k;
    client_header_buffer_size 1k;
	
    #ssl_session_cache    shared:SSL:1m;
    #ssl_session_timeout  5m;

    #ssl_ciphers  HIGH:!aNULL:!MD5;
    #ssl_prefer_server_ciphers  on;

    charset utf-8;
    location /tr_north{
        proxy_pass  http://tr_north;
        proxy_http_version 1.1;
        proxy_set_header   Connection       "";
        proxy_set_header   Host             $host;
        proxy_set_header   X-Real-IP        $remote_addr;
        proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;
         
        proxy_connect_timeout 6s;
        proxy_send_timeout 6s;
        proxy_read_timeout 6s;
        proxy_buffer_size 4k;
        proxy_buffers 32 4k;
        proxy_busy_buffers_size 64k;
        client_max_body_size 10m;
        client_body_buffer_size 128k;
    }
......