This indicates an attack attempt to exploit a Remote Code Execution vulnerability in Microsoft Windows Deployment Services.
A remote, unauthenticated attacker can exploit this vulnerability by sending a crafted TFTP read request to the target server and an unusually large number of ACKs with respect to the window size. Successful exploitation could result in the execution of arbitrary code as SYSTEM.
Microsoft Windows Server 2012
Microsoft Windows Server 2016
Microsoft Windows Server 2019
Microsoft Windows Server 2008 R2 Service Pack 1
Microsoft Windows Server 2008 Service Pack 2
Microsoft Windows Server 2012 R2
Microsoft Windows Server version 1803 (Server Core Installation)
System Compromise: Remote attackers can gain control of vulnerable systems.
Refer to the vendor supplied advisory for updates: