Microsoft has issued an emergency out-of-band security update to address a critical zero-day vulnerability known as “PrintNightmare” that affects the Windows Print Spooler service and can permit remote threat actors to run arbitrary code and take over vulnerable systems.

Tracked as CVE-2021-34527, the remote code execution flaw impacts all supported editions of Windows. Last week, Microsoft warned they had detected active exploitation attempts targeting the vulnerability.

According to Microsoft, not all versions of the update are available today as some packages are not quite ready for release.  The security updates for Windows Server 2016, Windows 10, version 1607, and Windows Server 2012 are currently delayed but expected soon. In the meantime, organizations may want to consider disabling the Print Spooler service (note: doing so will prevent the ability for users to print).

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