KB5012170: Take a closer look at this cumulative update

As you may already know, Microsoft rolled out its monthly Patch Tuesday updates just a few days ago, and you can find the full coverage here.

All operating systems are patched this month, including Windows 11, Windows 10, Windows 7, and Windows 8.1.

However, one of the most important releases this month is an extremely important fix related to Secure Boot DBX and its KB5012170 update.

Microsoft finally fixes critical Secure Boot GRUB vulnerability

In case you haven’t realized yet, Secure Boot disables signature database or DBX is actually a blacklist for UEFI executables Blocklist these executable files that are found to be bad.

The KB5012170 update mentioned above adds signatures for known vulnerable UEFI modules to DBX, meaning they will no longer be able to run after this update.

This time, the signatures are related to the GRand Unified Boot Loader (GRUB) vulnerability, also known as BootHole.

As we said, and as confirmed by Microsoft, this security update provides improvements to Secure Boot DBX for the supported Windows versions listed in the section.

The Redmond tech giant mentioned that these key changes include the following:

• Windows devices with Unified Extensible Firmware Interface (UEFI)-based firmware can Run with Secure Boot enabled. The Secure Boot Disable Signature Database (DBX) prevents UEFI modules from loading. This update adds modules to DBX.

You should also be aware that a security feature bypass vulnerability exists in Secure Boot. As a result, an attacker who successfully exploited this vulnerability could bypass Secure Boot and load untrusted software.

That being said, KB5012170 successfully addresses the vulnerability by adding signatures of known vulnerable UEFI modules to DBX.

What Windows versions does this update apply to?

The tech company also included in the official release notes that this update will resolve the issue for all versions.

So without further ado, we will say that KB5012170 addresses the following issues:

• Windows Server 2012
• Windows 8.1 and Windows Server 2012 R2
• Windows 10 Version 1507
• Windows 10 Version 1607 and Windows Server 2016
• Windows 10 Version 1809 and Windows Server 2019
• Windows 10, Version 20H2
• Windows 10, Version 21H1
• Windows 10, Version 21H2
• Windows Server 2022
• Windows 11, Version 21H2 (original version)
• Azure Stack HCI , Version 1809
• Azure Stack Data Frame, Version 1809 (ASDB)

Of course, this cumulative update can be downloaded as part of the Patch Tuesday package through Windows Update, but you can also download it from Get standalone updates from the Microsoft Update Catalog website.

What should I do if the installation of KB5012170 fails?

1. 1. Press Win I to access Settings.
   2. Select the System category and click Troubleshoot.
   3. Press the Other Troubleshooting button.
   4. Press the Run button next to Windows Update.

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