How to Fix Windows Update Error 0x800f0900?

Some Windows users are seeing the 0x800f0900 error code whenever they try to install a Cumulative Update on Windows 10. The 0x800f0900 translates into CBS_E_XML_PARSER_FAILURE (unexpected internal XML parser error) which is a signal that something is corrupted somewhere.

In most cases, affected users are reporting that the problem only occurs when they try to install the KB4464218 update.

Since the issue is somehow facilitated by some corrupted files that are stored locally, one way to circumvent the issue altogether is to use the Microsoft Update Catalog to install the update manually instead of relying on the Windows Update client – However, this will not allow you to discover the root cause of the issue.

In case you want to fix the underlying problem that’s causing the KB4464218, start simply by running the Windows Update Troubleshooter and see if the utility is capable of isolating the culprit and fixing it automatically. If that doesn’t work, move towards resetting the Windows Update component – You can either use the automated agent to do this or you can do the steps yourself (manually) from an elevated Command prompt.

However, in the event that you’re dealing with an advanced case of system file corruption, you might need to initiate a system-wide system corruption scan (using the SFC and DISM utilities).

In case the two conventional system file checkers (DISM and SFC) aren’t able to fix the issue for you, the final solution would be to refresh every OS component by doing a repair install (in-place repair).

Method 1: Installing the update manually

If you’re looking for a fix that will allow you to circumvent the issue regardless of the culprit that’s causing the problem, try downloading and installing the update that’s triggering the 0x800f0900 error manually.

You can do this easily by making use of the public Microsoft Update Catalog. Unless the service responsible for applying Windows Updates is affected, the instructions below should resolve the issue for you (a lot of users have used it successfully).

Here’s a quick step by step guide that will show  you how to use the Microsoft Update Catalog to find an install the missing update:

1. Open up your default browser and access this link (here) to access the web address of the Microsoft Update Catalog.
2. Once you’re inside the Microsoft Update Catalog, use the search function in the right corner of the screen to search for the update that’s triggering the 0x800f0900 error. Just type or paste the problematic update and press Enter to initiate the search.

   

   Note: Most affected users have confirmed that the problem only occurs with the KB4464218 cumulative update.

3. Once the results are in, look for the appropriate update by inspecting the CPU architecture and the Windows version it’s designed for.

   

   Note: If you don’t know your CPU or OS architecture, right-click on My Computer (This PC) and click on Properties. Next, look under System at the System Type – It will show the bit version of the operating system and the bit version of your CPU.

   

4. Once you manage to identify the appropriate update version, click on the Download button associated with the correct entry and wait patiently until the process is complete.
5. After the operation is complete, navigate to the location where you downloaded it. Once you’re inside, look for the .inf file and once you find it, right-click on it and choose Install from the newly appeared context menu.

   

6. Follow the on-screen instructions to complete the installation, then reboot your machine. At the next startup, the update should be already installed and Windows Update will no longer prompt you to install it.

In case you were looking for a different fix (one that will reveal the root cause of the issue) or the steps above ultimately fail with a different error, move down to the next potential fix below.

Method 2: Running the Windows Update Troubleshooter

Since the issue seems to be exclusive on Windows 10, the next logical step would be to see if your operating system doesn’t have the ability to resolve this issue by itself. Keep in mind that the built-in troubleshooter on Windows 10 is way more efficient than it was on Windows 7, or Windows 8.1

It will automatically scan the Windows Update component for any inconsistencies and will apply a viable repair strategy in case it recognizes a familiar scenario. We’ve found several user reports claiming that the Windows Update Troubleshooter fixed the 0x800f0900 error by resetting every involved WU component manually.

Here’s a quick step-by-step guide that will show you how to run the Windows Update troubleshooter from the Troubleshooting tab:

1. Press Windows key + R to open up a Run dialog box. Next, type ”ms-settings:troubleshoot’ and press Enter to open up the Troubleshooting tab of the Settings tab.

   

2. From the Troubleshooter tab, move down to the right-hand side section and scroll all the way down to the Get up and running section. Once you get there, click on Windows Update to select it, then click on Run the troubleshooter to launch the repair utility.

   

3. Once you’re inside the Windows Update troubleshooting menu, wait for the initial scan to complete, then click on Apply this fix in case a viable repair strategy was found.

   

4. After the correct repair strategy is applied, close the troubleshooting utility and reboot your machine.
5. Once it boots back up, open the Windows Update component once again and repeat the installation of the update that was previously failing with the 0x800f0900.

If the same problem is still occurring, move down to the next potential fix below.

Method 3: Resetting WU

In case the Windows Update troubleshooter was unable to fix the issue for you, it’s likely that you’re dealing with an underlying corruption file affecting the WU component – one that cannot be resolved conventionally. In this case, you should proceed by resetting every process, server, and installation involved in this operation.

When it comes to resetting every WU component, you have two approaches to choose from:

• Using the WU Reset Agent
• Resetting WU Manually

We’ve created two separate guides, providing steps for each of the two approaches. Feel free to follow whichever one you feel more comfortable with.

Using the Automated WU Reset Agent

1. Access this official Microsoft Technet page (here) and click on the Download button to download the Reset Windows Update Agent.

   

2. After the download is complete, extract the contents of the archive with a decompression utility. 
3. Once the operation is complete, double-click on ResetWUENG.exe and click Yes at the UAC (User Account Control) to open the installer with admin access.
4. Next, follow the on-screen instructions to run the script on your computer. Once it’s finished, reboot your machine and see if the problem is fixed by attempting to install the update that was previously failing with the error once again.

Resetting Windows Update manually (via CMD)

1. Open up a Run dialog box by pressing Windows key + R. Then, inside the text box, type ‘cmd’ and press Ctrl + Shift + Enter to open up an elevated CMD prompt.

   

   Note: At the User Account Control (UAC) prompt, click Yes to grant admin access.

2. Inside the elevated Command Prompt terminals, type the next set of commands (in whichever order), but make sure you press Enter after each one:

   net stop wuauserv
   net stop cryptSvc
   net stop bits
   net stop msiserver

   Note: Once you are finished with running these commands, you will have effectively disabled theWindows Update Services, MSI Installer, Cryptographic services, and BITS services.

3. Once every relevant Windows Update service is reset, run the following commands in whichever order to clear the two folders responsible for holding Windows Update Temporary data (SoftwareDistribution and Catroot2):

   ren C:\Windows\SoftwareDistribution SoftwareDistribution.old 
   ren C:\Windows\System32\catroot2 Catroot2.old

   Note: This operation will effectively remain the two folders since there is no way of deleting them conventionally. But this will ultimately help us to achieve the same end purpose since your OS will be forced to create new instances that were not tainted by any corruption.

4. Once the two processes have been cleared, run the following commands in the same elevated CMD terminal window and press Enter after each one to restart the services that you previously disabled at step 2:

   net start wuauserv
   net start cryptSvc
   net start bits
   net start msiserver

5. Once the operation is complete, restart your computer and see if you’re still encountering the 0x800f0900 error when you try to install a Windows Update.

In case the problem is still occurring, move down to the next potential fix below.

Method 4: Performing DISM and SFC scans

In case none of the methods above have allowed you to fix the 0x800f0900 error, it’s clear that you’re dealing with system file corruption. However, don’t despair, as Windows has a couple of built-in tools that will be able to fix most superficial corruption instances.

If this scenario is applicable, you should initiate two scans in quick succession in order to root out and fix those corrupted system files that end up interfering with the Windows Update component. SFC (System File Checker) and DISM (Deployment and Image Servicing and Deployment) should be used in this case to get the issue resolved.

First, you should start by running an SFC scan – This is an entirely local tool that scans for system file corruption and replace any detected instances with healthy copies fetched from an archive that is stored locally.

Once the operation is complete, restart your computer and see if the problem is resolved at the next computer startup.

In case the same problem is reappearing, perform a DISM scan. But keep in mind that in order to use it effectively, you will need a reliable internet connection since this tool relies on a sub-component of Windows Update to download healthy equivalents for the corrupted files that it identifies. At the end of this process, restart once again and see if the 0x800f0900 error is fixed.

In case the same problem is persisting, move down to the next potential fix below.

Method 5: Doing a Repair Install

If none of the methods above have allowed you to fix the issue, it means that you are facing an underlying corruption instance that requires extraordinary measures in order to resolve it. In case you’ve come so far without a result, your only hope at fixing the issue aside from doing a clean install.

But in case you want to avoid total data loss, doing a repair install (in-place upgrade) would be the preferred approach. This operation will allow you to reset every Windows component (including booting relation data) while allowing you to keep every bit of personal data including installed applications, games, videos, images, documents, etc.