resolveu adicionando "fastcgi_param SCRIPT_FILENAME"
Exemplo como abaixo
server {
listen 80;
root /var/www/joomla;
index index.php index.html index.htm;
server_name www.domain.com;
location / {
try_files $uri $uri/ /index.php?q=$request_uri;
}
location ~ \.php$ {
fastcgi_split_path_info ^(.+\.php)(/.+)$;
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
}
}