Over a year ago Microsoft Patch Tuesday updates for May 2019 addressed nearly 80 vulnerabilities, including the BlueKeep flaw.
The issue is a remote code execution flaw in Remote Desktop Services (RDS) that can be exploited by an unauthenticated attacker by connecting to the targeted system via the RDP and sending specially crafted requests.
As explained by Microsoft, this vulnerability could be exploited by malware with wormable capabilities, it could be exploited without user interaction, making it possible for malware to spread in an uncontrolled way into the target networks.