The new version fixes CVE-2018-5737 and CVE-2018-5736 + few bug fixes.
Release notes available here:
https://kb.isc.org/article/AA-01611/0/BIND-9.12.1-P2-Release-Notes.html
Release notes available here:
https://kb.isc.org/article/AA-01611/0/BIND-9.12.1-P2-Release-Notes.html