A third problem with Microsoft's August Windows 11 update has surfaced this week: on some PCs, the KB5121003 patch is corrupting the small credential file Windows uses to remember your sign-in PIN, locking users out at the login screen even after they set a new PIN. Microsoft has already opened a formal investigation into a separate gaming issue from the same update, and repair shops are now seeing PIN lockouts pile on top of that.
What's happening
The August 2026 Patch Tuesday update, KB5121003, rolled out on August 11, bringing the OS to Build 26200.9168 if you are on version 25H2 or Build 26100.9168 on PCs with version 24H2 . It's a large security release — Windows 11's August 2026 Patch Tuesday update is available for everyone and is yet another massive release, patching up to 421 security issues, and Microsoft's advisory tells users not to delay it by more than 3 days .
The first wave of problems was gaming-related. Microsoft said it received reports of issues involving inability to run games as expected following the August 11 update, is investigating whether the issue is caused by Microsoft, and will provide an update when more information is available . Embark Studios has linked crashes in its games to the inpoutx64.sys driver, though it isn't yet clear what KB5121003 changed that broke compatibility .
On top of the gaming crashes, two more issues surfaced on August 19 and 20. The most disruptive is a PIN sign-in lockout: since KB5121003 went on, some PCs won't accept the PIN at the login screen any more, Windows offers to set up a new one, you do that and it works, then you restart the machine and you're locked out again . The root cause appears to be that Windows keeps your PIN as a small credential file rather than the PIN itself, and this update is corrupting it . A separate cosmetic bug is also making Windows Security falsely claim virus protection is off — the notification claiming that "Virus protection is turned off" following the August 2026 update is a known UI bug, it is not malware, and Microsoft Defender is still active and protecting the system in the background .
How to get back in if your PIN stops working
Do not remove the update to "fix" the PIN. KB5121003 closes serious security holes, and rolling it back leaves your machine exposed. Instead, sign in with your password on the login screen: on the login screen there's a Sign-in options link just below the PIN box — click it, pick the key icon for your password, and type that; password sign-in is completely unaffected by this bug, only the PIN is broken .
There's one common snag. A lot of people set a PIN years ago and haven't typed their actual account password since, so they've genuinely forgotten it — if that's you, you can reset it from your phone or another computer at account.microsoft.com, then use the new password to get into your PC; do that before you next shut down, not after . If you're already locked out and can't remember the Microsoft account password, that's the point where most people end up needing help from a Windows repair technician to get back into the machine without wiping it.
Avoid the temptation to reset or reinstall Windows to work around this. A clean install will wipe your files, and if you don't have a current backup, you may then need help to recover documents and photos off the old drive.
Should you still install the update?
Yes. According to Microsoft, the Windows 11 August 2026 Update fixed at least 37 remote code execution bugs and five elevation-of-privilege bugs , and one of the flaws is already being used in real attacks. The gaming crashes and the PIN bug are real annoyances, but neither is a reason to leave a PC unpatched against actively-exploited vulnerabilities. If your PC is a daily driver you can't afford to have offline, install the update during a window when you have time to sign in with a password if the PIN bug hits you, and make sure you know your Microsoft account password before you reboot.
What This Means for York, PA
If you're in York County and your laptop or desktop is stuck at the PIN screen after this month's Windows update — or throwing a fake "virus protection off" warning — bring it into York Computer Repair at 2069 Carlisle Rd. We can get you signed back in, verify the update installed cleanly, and confirm your antivirus is actually running, usually same-day.
Sources
- August 2026 Windows Update — Known Problems and Fixes
- Microsoft says August Windows updates may cause gaming issues
- Windows 11's August update is breaking games, and Microsoft is investigating
- Windows 11 Update Error: How to Fix August 2026 Bugs
- Microsoft warns users to install Windows 11's latest update within 3 days