Nginx 502 Bad Gateway error ONLY in Firefox

Question

I am running a website locally, all the traffic is routed through NGinx which then dispatches requests to PHP pages to Apache and serves static files. Works perfectly in Chrome

Answer 1

Increasing the size of your proxy buffers solves this issue. Firefox allows large cookies (up to 4k each) that are attached to every request. The Nginx default config has small buffers (only 4k). If your traffic uses big cookies, you will see the error "upstream sent too big header while reading response header" in your nginx error log, and Nginx will return a http 502 error to the client. What happened is Nginx ran out of buffer space while parsing and processing the request.

To solve this, change your nginx.conf file

proxy_buffers 8 16k; proxy_buffer_size 32k;

-or-

fastcgi_buffers 8 16k; fastcgi_buffer_size 32k;