Microsoft has started rolling out an emergency Windows patch to address a critical flaw in the Windows Print Spooler service. The vulnerability called “PrintNightmare,” that was discovered last week, allows attackers to remotely execute malicious code with system privileges and install programs, make changes in the existing programs, and create new accounts with full user rights.

The list of Windows versions that have received the security updates to patch the PrintNightmare vulnerability comprises Windows Server 2004, Windows Server 2008, Windows Server 2012, Windows Server 2012 R2, Windows Server 2016, Windows Server 2019, Windows 7, Windows RT 8.1, Windows 8.1, and Windows 10.

Since the Windows Print Spooler service exists on all Windows versions, the vulnerability has impacted all Windows machines. However, the security updates list is currently limited to a few versions initially. Microsoft said that it would update the remaining Windows versions soon.

“We recommend that you install these updates immediately,” says Microsoft. “The security updates released on and after July 6, 2021 contain protections for CVE-2021-1675 and the additional remote code execution exploit in the Windows Print Spooler service known as ‘PrintNightmare’, documented in CVE-2021-34527.”

Meanwhile, users on a Windows machine that is yet to receive the security fix are recommended to manually disable the Print Spooler service or disable inbound remote printing. The Print Spooler can be disabled by passing the “Stop-Service -Name Spooler -Force” and “Set-Service -Name Spooler -StartupType Disabled” commands through PowerShell.