A memory corruption vulnerability exists in the Windows Server DHCP service when processing specially crafted packets. An attacker who successfully exploited the vulnerability could cause the DHCP server service to stop responding. To exploit the vulnerability, a remote unauthenticated attacker could send a specially crafted packet to an affected DHCP server. The security update addresses the vulnerability by correcting how DHCP servers handle network packets.
https://www.tenable.com/blog/tenable-roundup-for-microsoft-s-august-2019-patch-tuesday-dejablue
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1212