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Microsoft has released out-of-band  to address a remote code execution vulnerability — known as PrintNightmare (CVE-2021-34527) — in the Windows Print spooler service. The Computer Emergency Response Team Coordination Center (CERT/CC), part of the Software Engineering Institute at Carnegie Mellon University, last week reported a critical RCE vulnerability impacting the Windows Print Spooler service that allows a remote authenticated attacker to execute arbitrary code with system privileges on a vulnerable system.

The updates are cumulative and contain all previous fixes, as well as protections for CVE-2021-1675. The updates do not include Windows 10 version 1607, Windows Server 2012 or Windows Server 2016 — Microsoft states updates for these versions are forthcoming. According to CERT/CC, “the Microsoft update for CVE-2021-34527 only appears to address the Remote Code Execution (RCE via SMB and RPC) variants of the PrintNightmare, and not the Local Privilege Escalation (LPE) variant.” See for workarounds for the LPE variant. 

The Cybersecurity & Infrastructure Security Agency encourages users and administrators to review the Microsoft security updates as well as CERT/CC Vulnerability Note VU #383432 and apply the necessary updates or workarounds. For additional background, see .