How to fix
KB5021233 fails to install
on Windows

The newest Windows update, KB5021233, keeps failing to install for me. I have never encountered something before, so I would appreciate some assistance on this matter, please. I'm running Windows version 22H2.

Windows updates are regular releases of new features, bug fixes, and security updates for the Windows operating system. These updates are essential for the smooth and secure running of your computer, and it is important to keep your system up to date. Windows updates can be installed automatically or manually, depending on your settings.

Just like any other Patch Tuesday, KB5021233 was released for Windows 10 (OS Builds 19042.2364, 19043.2364, 19044.2364, and 19045.2364) versions 21H1, 21H2, and 22H2 on December 13.[ref en-1]

Just like KB5021255 for Windows 11, this one is meant to patch several security vulnerabilities[ref en-2] present in both versions of the OS. Additionally, the more notable changes include Cortana's removal from the taskbar and the search box being visible if the taskbar is moved to the top.

Security updates are particularly important and should be implemented as soon as possible, although not everybody could do it, as users reported KB5021233 not installing issues. While an error code may be displayed when this happens, some users reported that Windows simply says it will try again later, although this rarely helps.

Windows update issues are a common occurrence, and most users will experience them at some point during their time using a PC. In many cases, these errors resolve on their own - in this case, the reason being unstable internet connections or issues with Microsoft's servers. Unfortunately, some people can't get the updates to install, and it can become a major issue.

If you can't install KB5021233, we provide several solutions for this issue below - we explain how to fix incorrectly configured related services, bugged[ref en-3] update file caches, space issues, system file corruption, and more. Note that many of the troubleshooting steps below can be covered by an automatic PC repair tool [d1], which we highly recommend trying.

Fix 1. Troubleshoot

Troubleshooters are great built-in tools that allow users to find and repair some common issues they are having with their PCs, including Windows updates. Thus, we recommend running a Windows update troubleshooter as the first option.

• Type Troubleshoot in Windows search and press Enter
• On the right side of the window, click Additional troubleshooters
• Scroll down to find Windows update and click it
• Click Run the troubleshooter - let the process run
• Once finished, apply the suggested fixes and reboot your system.

Fix 2. Make sure you have enough space

Disk Cleanup is one of the options you could use if KB5021233 fails to install due to a lack of space on the system. Accumulation of temporary or other junk files can be the cause for this - you can remove them as follows:

• Type Disk Cleanup in Windows search and hit Enter
• If your Windows is installed on drive C, pick it from the list (should be by default) and press OK
• Click Clean up system files
• Select your main disk again and click OK
• Here, select the largest portions of the data used - these typically include Temporary Internet Files, Windows Update, Temporary Files, Recycle Bin, Delivery Optimization Files, and others.
• Click OK - the process should be finished shortly.

Fix 3. Check your system files with SFC and DISM

Corrupted system files or registries are among the most common reasons why Windows updates fail. You can fix them as follows:

• Type cmd in Windows search
• Right-click on Command Prompt search result and select Run as administrator
• UAC (User Account Control) will ask whether it can make changes, click Yes
• Next, copy and paste the following command and press Enter:
  sfc /scannow
• Once done, run the following commands as well:
  dism /online /cleanup-image /scanhealth
  dism /online /cleanup-image /checkhealth
  dism /online /cleanup-image /restorehealth
• Restart your system.

Fix 4. Install the update manually

You can try installing the update manually:

• Open your browser and go to Microsoft Update Catalog
• Copy and paste the relevant KB number which failed to install (in this case, KB5021233) to the search box and click Search
• Here, find the correct version of the update for your operating system (to check this, right-click on Start and pick System. Under Device specifications and check the System type)
• Click Download and follow the on-screen instructions
• Reboot the system once the process is finished.

Fix 5. Check relevant services

Windows update process requires certain services (namely, BITS and Windows Update) to run to succeed. If they are already running, you can restart them instead:

• Type in Services in Windows search and press Enter
• Scroll down to locate Background Intelligent Transfer Service (BITS)
• If it is already running, right-click and pick Restart
• if the service is not running, double-click it, select Automatic under the Startup type from the drop-down menu
• Click Start, Apply, and OK

Fix 6. Reset Windows update components

• Open Command Prompt (Admin) as explained above
• Copy and paste the following commands, pressing Enter each time:
  net stop wuauserv
  net stop cryptSvc
  net stop bits
  net stop msiserver
• Press Win + E to open File Explorer
• Go to the following locations and delete the contents of these folders:
  C:\Windows\System32\catroot2
  C:\Windows\SoftwareDistribution

• Open Command Prompt again and paste these command lines:
  net start wuauserv
  net start cryptSvc
  net start bits
  net start msiserver
  
• Restart your system.

Fix 7. Try in-place upgrade

You can always rely on an official Microsoft tool to update your system to the latest version.

• Visit the official Microsoft website and download Windows 10 installation media
• Launch the installer and click Yes when the User Account Control window shows up
• Agree to the terms and click Next
• Select Upgrade this PC now and click Next
• Wait till Windows downloads all the necessary files
• Agree to terms once again and click Next
• Before installing, make sure that you are happy with your choices (otherwise, you can click Change what to keep option)
• Finally, click Install to begin the upgrade process.