The U.S. National Security Agency (NSA) on Tuesday urged Windows users and administrators to immediately address the vulnerability tracked as BlueKeep and CVE-2019-0708.

Many experts agree that it’s only a matter of time until the flaw is exploited in the wild. An increasing number of proof-of-concept (PoC) exploits have been developed and one researcher even claims to have created a module for the Metasploit penetration testing framework. Fortunately, a weaponized and fully working exploit that can achieve remote code execution has yet to be made public.

However, one researcher reported finding nearly one million vulnerable devices online and cybersecurity organizations have already seen scanning activity targeting CVE-2019-0708.

“This is the type of vulnerability that malicious cyber actors frequently exploit through the use of software code that specifically targets the vulnerability. For example, the vulnerability could be exploited to conduct denial of service attacks. It is likely only a matter of time before remote exploitation code is widely available for this vulnerability. NSA is concerned that malicious cyber actors will use the vulnerability in ransomware and exploit kits containing other known exploits, increasing capabilities against other unpatched systems,” the NSA said in an advisory.

“NSA urges everyone to invest the time and resources to know your network and run supported operating systems with the latest patches,” the agency added. “This is critical not just for NSA’s protection of National Security Systems but for all networks.”

BlueKeep impacts the Windows Remote Desktop Services (RDS) and it was addressed by Microsoft with its May 2019 Patch Tuesday updates. The vulnerability has been described by the tech giant as wormable and it can be leveraged by malware to spread similar to the way the notorious WannaCry ransomware did back in 2017 through the EternalBlue exploit.

An unauthenticated attacker can leverage the flaw to execute arbitrary code and take control of a device without any user interaction. Microsoft has released patches for Windows 7, Server 2008, XP and Server 2003.

In addition to installing the patches from Microsoft, Windows users can prevent attacks by configuring firewalls to block TCP port 3389, disabling RDS if it’s not needed, and for some versions of Windows, enabling Network Level Authentication (NLA).

Related: Microsoft Reminds Users to Patch Wormable 'BlueKeep' Vulnerability