Steps to reproduce the issue

1. On the backend go to Artciles -> Media
2. Try to open a directory with non-latin characters (for example: "2017/2017-01-styczeń")

Expected result

The directory should open

Actual result

Being redirected to images root directory

System information (as much as possible)

Noticed since Joomla 3.5. Still happens in 3.7. Seems to be browser independent. Happened in PHP 5.2-7.0.

Additional comments

You could also navigate to a folder directly via /administrator/index.php?option=com_media&view=mediaList&tmpl=component&folder=2017/2017-01-stycze%C5%84

Possible solution

Seems to be a regex problem with JInput filter "path" that is used in list.php model of com_media. Regex:
$pattern = '/^[A-Za-z0-9_-]+[A-Za-z0-9_\.-]*([\\\\\/][A-Za-z0-9_-]+[A-Za-z0-9_\.-]*)*$/';