On another forum topic, @EvanCooper says that version 8.5.7 should be enough to solve my issue.
Other question, as my website is dawn, I think I need to use this method to upgrade my 8.3.1 C5 version :
### Replacing Original Concrete Directory (Version 8+)
** Download version 8.5.7*
** Replace the concrete directory in web root.*
** Empty updates directory.*
** Delete application/config/update.php.*
** Replace composer.json and composer.lock (if pre-8.2.0).*
** Visit your site; Concrete will run required database migrations.*
Do you confirm that it will work even if my website is currently dawn with a MySQL issue ?