Microsoft has released an emergency out-of-band security update to address a critical zero-day vulnerability - PrintNightmare. It is a reminder that this flaw impacts the Windows Print Spooler service, which can allow threat actor to execute code remotely and take over vulnerable systems.

The flaw that has received the identifier CVE-2021-34527 and CVSS score of 8.8, threatens all supported editions of the Windows operating system.

It is worth noting that the threat actors with this flaw could not only execute code remotely, but also could elevate privileges up to SYSTEM.

"The previously released patch appears to address RCE bug of the PrintNightmare, and not the local privilege escalation issue,” Will Dormann from Microsoft said.

Microsoft suggested the following measures as workarounds: stop and deactivate the Print Spooler service. Now users of the systems listed below should install a new update:

Windows Server 2019

Windows Server 2012 R2

Windows Server 2008

Windows 8.1;

Windows RT 8.1;

Windows 10 (versions 21H1, 20H2, 2004, 1909, 1809, 1803, and 1507).

Source: anti-malware.ru