An attacker who is permitted to send zone data to a server via zone transfer can exploit this to intentionally trigger the assertion failure with a specially constructed zone, denying service to clients.
https://usn.ubuntu.com/4399-1/
https://security.netapp.com/advisory/ntap-20200625-0003/
https://kb.isc.org/docs/cve-2020-8618
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00044.html
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00041.html