PrintNightmare(CVE-2021-34527): Microsoft Releases Out-of-Band Security Updates

by CIRT Team

07 Jul 2021

in CVE, Security Advisories & Alerts

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Microsoft has released the KB5004945 emergency security update to fix the actively exploited PrintNightmare zero-day vulnerability in the Windows Print Spooler service impacting all Windows versions. However, the patch is incomplete and the vulnerability can still be locally exploited to gain SYSTEM privileges.

The remote code execution bug (tracked as CVE-2021-34527) allows attackers to take over affected servers via remote code execution (RCE) with SYSTEM privileges, as it will enable them to install programs, view, change, or delete data, and create new accounts with full user rights.

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.

Detailed instructions on how to install these out-of-band security updates please check the following URL:

https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-34527

Reference URL:

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527
https://nvd.nist.gov/vuln/detail/CVE-2021-34527
https://us-cert.cisa.gov/ncas/current-activity/2021/07/06/microsoft-releases-out-band-security-updates-printnightmare
https://www.bleepingcomputer.com/news/security/microsoft-pushes-emergency-update-for-windows-printnightmare-zero-day/