elementary OS Juno is based on Ubuntu 18.04 LTS. Any system update to core Ubuntu will have affect on elementary OS too. It means when Ubuntu 18.04 has been patched with latest sudo, it will be on elementary OS too. You need update your system then to get the new patch.
From your shared link, It's telling:
The problem can be corrected by updating your system to the following package versions:
Ubuntu 18.04 LTS
sudo - 1.8.21p2-3ubuntu1.1
sudo-ldap - 1.8.21p2-3ubuntu1.1
And my eOS sudo is:
$ dpkg-query --showformat='${Package}\t${Version}\n' --show sudo
sudo 1.8.21p2-3ubuntu1.1
It's already updated with patched version. Probably you are safe too.