Microsoft issues out-of-band patch for PrintNightmare

Posted on Wednesday, July 07 2021 @ 9:30 CEST by Thomas De Maesschalck
Last week, warnings went out about a dangerous vulnerability in the Windows Print Spooler service. Called PrintNightmare, this bug allowed attackers to execute code with system-level privilege. Mitigation techniques basically consisted of switching off remote printing capabilities -- not ideal for businesses, but doable if we're talking about a server that's not used for printing.

Fortunately, there's already a patch for this critical flaw. Microsoft has issued updates for basically every supported version of Windows.
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.
This out-of-cycle patch from Microsoft will be installed automatically via Windows Update.

About the Author

Thomas De Maesschalck

Thomas has been messing with computer since early childhood and firmly believes the Internet is the best thing since sliced bread. Enjoys playing with new tech, is fascinated by science, and passionate about financial markets. When not behind a computer, he can be found with running shoes on or lifting heavy weights in the weight room.

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