July 6, 2021 Security Update (KB5004961) Out-of-band

Improvements and fixes

This security update includes quality improvements. Key changes include:

• Addresses a remote code execution exploit in the Windows Print Spooler service, known as “PrintNightmare”, as documented in CVE-2021-34527. After installing this and later Windows updates, users who are not administrators can only install signed print drivers to a print server. By default, administrators can install signed and unsigned printer drivers to a print server. The installed root certificates in the system’s Trusted Root Certification Authorities trusts signed drivers. Microsoft recommends that you immediately install this update on all supported Windows client and server operating system, starting with devices that currently host the print server role. You also have the option to configure the RestrictDriverInstallationToAdministrators registry setting to prevent non-administrators from installing signed printer drivers on a print server. For more information, see KB5005010.

For more information about the resolved security vulnerabilities, please refer to the Security Update Guide.

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Known issues in this update

How to get this update

The July 6, 2021 security update (KB5004961) for Azure Stack HCI is delivered from the release channels below. To install it on your Azure Stack HCI cluster, see Update Azure Stack HCI clusters.

Install this update