nginx error connect to php5-fpm.sock failed (13: Permission denied)

All the fixes currently mentioned here basically enable the security hole all over again.

What I ended up doing is adding the following lines to my PHP-FPM configuration file.

listen.owner = www-data
listen.group = www-data

Make sure that www-data is actually the user the nginx worker is running as. For debian it's www-data by default.

Doing it this way does not enable the security problem that this change was supposed to fix.

I had a similar error after php update. PHP fixed a security bug where o had rw permission to the socket file.

1. Open /etc/php5/fpm/pool.d/www.conf or /etc/php/7.0/fpm/pool.d/www.conf, depending on your version.

2. Uncomment all permission lines, like:

   listen.owner = www-data
   listen.group = www-data
   listen.mode = 0660
   

3. Restart fpm - sudo service php5-fpm restart or sudo service php7.0-fpm restart

Note: if your webserver runs as user other than www-data, you will need to update the www.conf file accordingly