A memory corruption vulnerability exists in the Windows Server DHCP service when an attacker sends specially crafted packets to a DHCP failover server, aka 'Windows DHCP Server Remote Code Execution Vulnerability'.
https://www.tenable.com/blog/microsoft-s-july-2019-patch-tuesday-what-you-need-to-know
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-0785