A memory corruption vulnerability exists in the Windows Server DHCP service when an attacker sends specially crafted packets to a DHCP server. An attacker who successfully exploited the vulnerability could run arbitrary code on the DHCP server. To exploit the vulnerability, an attacker could send a specially crafted packet to a 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-2019-1213