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Microsoft has released out-of-band security updates to address a remote code execution (RCE) vulnerability—known as PrintNightmare (CVE-2021-34527)—in the Windows Print spooler service. According to the CERT Coordination Center (CERT/CC), “The Microsoft Windows Print Spooler service fails to restrict access to functionality that allows users to add printers and related drivers, which can allow 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. Note: 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 CERT/CC Vulnerability Note VU #383432 for workarounds for the LPE variant.
CISA 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 CISA’s initial Current Activity on PrintNightmare.
Brought to you by Dr. Ware, Microsoft Office 365 Silver Partner, Charleston SC.