I keep getting this result in Avast Mobile Security for Android when I scan the wi-fi connection. I notified Avast about a similar false positive on my laptop/desktop a few months back [https://forum.avast.com/index.php?topic=182804.msg1291674] which Avast resolved after realizing it was an error on their end due to a response from my router. The next update fixed that on both my laptop & desktop. However when scanning using the program on Android devices (both phones & tablets) on the same network I get the same exact results (weak password, etc).
As a heads up I also noticed similar results on another network that uses the same brand of router, so I’m guessing the issue is along similar lines to the other fix.