In case you have installed Kali Linux using an older ISO, you can easily update all packages doing like this:
# update the installed packages john@kali:~$ sudo apt update # upgrade kali linux john@kali:~$ sudo apt full-upgrade -y
As Kali Linux is continuously providing updated packages you might want to do the update every now and then. I usually do that once a week.
Hint | You can shorten the above statements in one line and just type:
john@kali:~$ sudo apt update && apt -y full-upgrade
 https://kali.org/docs/general-use/updating-kali/ (Official Kali Linux Documentation)