FTP / Install / Automatic Upgrade failure

This is true for all version. Whenever I try to do any upgrade from the admin panel I get the following error:

Warning: tmpfile() has been disabled for security reasons in /home/…/…/wp-admin/includes/class-wp-filesystem-ftpext.php on line 120

I understand this to be an issue on my server side and not within the WP code. It is not possible to activate this on the server, due to the host’s security policies.

Is there a workaround?