KB5004237 was Microsoft’s July 13, 2021 monthly cumulative security update for Windows 10 versions 2004, 20H2 and 21H1. On Windows 10 21H1 x64 it installed build 19043.1110; it was not a feature upgrade. In 2026, it is a historical update rather than a download target: Microsoft says it is no longer available through the Update Catalog or other release channels and recommends installing the latest applicable security-quality update instead.
KB5004237 at a glance
| Item | Details |
|---|---|
| Release date | July 13, 2021 |
| Update type | Monthly cumulative security and quality update |
| Windows 10 2004 | Build 19041.1110 |
| Windows 10 20H2 | Build 19042.1110 |
| Windows 10 21H1 | Build 19043.1110 |
| Architectures | Packages varied by architecture; the AnandTech title refers to x64 |
Microsoft’s release notes cover the operating-system version and edition, not just the wording of the forum title. Separate x86 and ARM64 packages existed where applicable. The original title’s “21H1for” is simply a missing space.
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See Microsoft’s release information: KB5004237 release notes.
What the update changed
Printing and security improvements
- Microsoft fixed a printing problem affecting some printers, particularly USB-connected receipt and label printers.
- It added security improvements to basic Windows operations and to username and password verification.
- It included changes related to Kerberos security enforcement for CVE-2020-17049.
- The release included the Adobe Flash removal package.
These notes do not mean KB5004237 fixed every PrintNightmare-related problem. Microsoft issued several separate emergency and out-of-band printing updates during that period; this cumulative update’s documented printing change was specific to the issue described in its release notes.
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What it did not change
For Windows 10 21H1, Microsoft listed no additional version-specific issue beyond the shared improvements. The update moved the system to build 19043.1110; it did not convert 21H1 into another feature release.
Known issues Microsoft documented
Japanese IME Furigana generation
When Microsoft’s Japanese Input Method Editor was used to enter Kanji in an application that automatically generated Furigana, the generated reading could be incorrect. Microsoft advised affected users to enter Furigana manually. The issue was resolved in KB5005101. Details are listed in Microsoft’s KB5004237 support article.
Custom offline media and Edge Legacy
Some devices created from custom offline media or custom ISO images could lose Microsoft Edge Legacy without receiving the replacement Microsoft Edge. This applied when an administrator slipstreamed KB5004237 without first integrating the standalone servicing stack update released March 29, 2021, or a later SSU.
Devices updated directly through Windows Update were not affected by this custom-image condition. If you build deployment media, integrate the required servicing-stack update before the cumulative update.
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Microsoft Q&A reports associated with KB5004237 include repeated failures with error 0x80073712. That code commonly points to missing or corrupted update files or a damaged Windows component store, but the discussion does not establish one universal KB5004237 defect.
- Component-store corruption or an incomplete servicing state
- Damaged or stale Windows Update downloads
- Interrupted earlier updates or insufficient free space
- Third-party security software or drivers interfering with servicing
- A package mismatch involving architecture, edition, build, prerequisites or supersedence
- Incorrect servicing order in a custom image
“Not applicable to this computer” usually means that the package is already installed or superseded, or that its version, architecture, edition or prerequisites do not match. It does not by itself prove that Windows is damaged.
Preflight checks before repairing Windows Update
- Press Win + R, enter
winver, and record the Windows version and build. - Open Settings → Update & Security → Windows Update → View update history and search for KB5004237.
- Open Settings → System → About (or System → About) and confirm whether the device is x64-based.
- Back up important files before component repair or an in-place repair installation.
- Disconnect unnecessary peripherals if installation repeatedly fails.
- Investigate third-party antivirus or endpoint controls as a possible interference source; do not leave protection permanently disabled.
How to troubleshoot a failed installation
1. Restart and retry through Windows Update
Restart normally, let Windows Update check again, and avoid forcing a shutdown during installation or reboot. If the update is already superseded, install the latest applicable cumulative update instead of trying to force this 2021 package.
2. Repair the online component store with DISM
Open Command Prompt or Windows PowerShell as administrator and run:
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DISM /Online /Cleanup-Image /RestoreHealthWait for completion, restart, and retry Windows Update. One Microsoft Q&A participant reported that DISM was the step after which KB5004237 installed, but that is an individual report, not a guarantee.
3. Check protected system files
After DISM completes successfully, run:
sfc /scannowRestart again before retrying. DISM repairs the servicing component store; SFC checks protected Windows system files.
4. Reset the Windows Update download state
If the failure suggests a damaged or repeatedly reused download, open an elevated command window and stop the services:
net stop bits
net stop wuauserv
net stop cryptsvcClear or rename the Windows Update download cache, then restart the services:
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net start wuauserv
net start bitsReboot and try again. Cache changes can affect delivery optimization, WSUS, Configuration Manager and other enterprise controls, so administrators should follow their management policy rather than deleting caches casually.
5. Validate a package for historical recovery
If you are servicing a preserved 2021 system, verify all of the following before using a manually obtained package:
- Windows version is 21H1 and the build branch is 19043.
- The architecture is x64, not x86 or ARM64.
- The edition and servicing prerequisites match.
- The package has not already been superseded or installed.
The Microsoft Update Catalog search can show similarly named preview or .NET packages. KB5004296 was a July 2021 preview update, and KB5003537 was a .NET Framework update; neither is KB5004237.
6. Use an in-place repair installation only as a later step
If DISM, SFC, cache repair and normal Windows Update troubleshooting fail, back up data, confirm the edition and language, and use current Microsoft installation media. Choose the option to keep personal files and applications where available. An in-place repair is a broad recovery measure, not a first response to one obsolete update.
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What forum users reported
The AnandTech discussion is useful historical context, but its posts are anecdotal. Participants reported installation or reboot times ranging from about one minute to roughly 15 minutes. Others discussed cleanup-file sizes, disk space and sound-card settings. These observations varied by machine and do not demonstrate that KB5004237 universally caused slowdowns, added a particular amount of disk usage or changed audio settings.
The thread also contains opinions about utilities such as CCleaner. It does not establish that third-party cleaners are needed, and they should not replace servicing repair or a current Windows update.
Read the discussion at AnandTech.
Should you download KB5004237 now?
Generally, no. Microsoft’s current notice says that since September 12, 2023, KB5004237 is no longer available through the Microsoft Update Catalog or other release channels and is available only through Windows Update. Microsoft recommends installing the latest applicable security-quality update instead.
| Situation | Best action |
|---|---|
| Windows Update offers KB5004237 in its original 2021 context | Install it if the machine is an affected Windows version and no compatibility error is reported. |
| The update takes several minutes | Allow the installation to finish; duration alone is not evidence of failure. |
| Installation returns 0x80073712 | Check the build and history, then use DISM, SFC and, if appropriate, a controlled cache reset. |
| You are using Windows 10 in 2026 | Install the latest applicable update offered for the device and plan an upgrade or migration from an obsolete installation where appropriate. |
Windows Update is usually safer than manual installation because it selects applicable packages and handles prerequisites. Manual Catalog deployment is useful for controlled offline servicing, but it increases the chance of architecture, version and supersedence errors and cannot repair a damaged component store.
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