Update 2026-10 Security Update (KB5127648) (26100.9711) is failing every time and causing a boot loop.

Question

Update 2026-10 Security Update (KB5127648) (26100.9711) is failing every time and causing a boot loop.

Alfie 0

Each time the above update tries to install it hits 0%, says something went wrong and tries to undo the changes. It seems to not go through correctly and boots to the recovery environment. I tried rolling back to a restore point and that failed. I tried to reinstall windows from a USB and when clicking the button to do so on the recovery environment it just sits loading then backs out with no error before I can choose my USB.

If the PC is shut off and restarted a couple of times it will ignore the update and boot to windows and function with no issue until it tries to install the update again.

What I've done so far:

Checked Windows Update in Settings.
The October 2026 security update KB5127648, build 26100.9711, was offered.
The update repeatedly failed during installation and rolled back.
Windows Update later showed the update as Pending restart, with an orange restart indicator.
Update History showed KB5127648 as “Successfully installed on 02/11/2026” (2 November 2026, using UK date format).
I have shut down and powered the PC back on, but I have not confirmed the update by using Update and restart after recovering from the problem.

There is a discrepancy between the update history and the currently active build: winver and Settings still showed 26100.8875, rather than the target 26100.9711.

I ran the following Windows repair/checking tools:

DISM online repair: Ran DISM with /RestoreHealth. It initially returned RPC error 1726, but I subsequently managed to run the repair successfully which found and restored corrupted files.

System File Checker (SFC): The first scan found and repaired corruption. A later scan reported that Windows Resource Protection did not find any integrity violations.

CHKDSK: Ran a disk check, which reported no issues.

Despite these checks and fixes, I have not yet re-ran the update to avoid further issues.

I opened Reliability Monitor using perfmon /rel and found several crashes and unexpected shutdowns on 2 November 2026.

There were two “Windows Modules Installer Worker stopped working” events.

First crash:

Application: TiWorker.exe

Application version: 10.0.26100.9703

Faulting module: ntdll.dll

Faulting module version: 10.0.26100.8875

Problem Event Name: BEX64

Exception code: c0000409

Exception data: 0000000000000002

Second crash:

Application: TiWorker.exe

Path included the servicing-stack folder for version 10.0.26100.9703 under C:\Windows\WinSxS

Faulting module: dpx.dll

Faulting module version: 10.0.26100.8875

Problem Event Name: BEX64

Exception code: c0000409

Exception data: 0000000000000002

These events appear to be related to Windows servicing activity, but I do not know whether they are the cause of the update failure or a consequence of it.

Is this a known issue, and are there any fixes or advice what to do next? Thanks in advnace.

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1 answer

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Answer 1

TaoLi 119.5K Independent Advisor

Hi, the old build number means the update hasn’t taken effect. Since you’ve already run DISM and SFC, I’d try a repair install from the Windows desktop.

Back up your files, then open your Windows 11 USB in File Explorer >> run setup.exe >> choose Keep personal files and apps >> Install. This preserves your files and installed apps.

Start this while signed into Windows, without using the recovery menu. If the keep option is unavailable or Setup shows an error, stop and share the message so I can follow up.

Alfie 0 Reputation points

2026-11-04T13:08:09.78+00:00

Thank you for the reply, it has been stuck on Getting Updates - "Checking for Updates: 46%" for some time before I've gotten to the point of choosing to keep files and starting the repair.

Is it worth trying to put the update through normally with a restart as I've not tried since SFC and DISM repaired files?
TaoLi 119.5K Reputation points Independent Advisor

2026-11-04T13:17:29.48+00:00

Yes, I’d try one normal update restart now that DISM and SFC have repaired files.

Cancel Windows Setup and let it close completely, back up important files, then select Start >> Power >> Update and restart. Let it finish or roll back without forcing the PC off.

If it fails again and Windows recovers, reopen setup.exe >> Change how Setup downloads updates >> Not right now. This skips the update check that’s stalling. Continue only with Keep personal files and apps selected.
Alfie 0 Reputation points

2026-11-04T13:20:07.56+00:00

Thank you, I'll put that through shortly and report back.
TaoLi 119.5K Reputation points Independent Advisor

2026-11-04T13:31:22.3233333+00:00

You're welcome. I'm happy to help you.
Alfie 0 Reputation points

2026-11-04T14:01:23.85+00:00

Thanks for your patience. I restarted and the update failed again with a different error code this time "SYSTEM_SERVICE_EXCEPTION (0x38)" but it booted without a blue screen or entering recovery environment for a short moment. It then shut itself down with a hypervisor error and booted back up again.

Currently the update now says it has actually failed within the Windows Update section saying the following:2026-10 Security Update (KB5127648) (26100.9711)
Install error - 0x800f0839

Should I proceed with the reinstall from the USB I created with the media creation tool?
TaoLi 119.5K Reputation points Independent Advisor

2026-11-04T14:25:54.31+00:00
Before starting the reinstall, please share these files so I can check the crashes and installation failure:

The newest 2–3 .dmp files from C:\Windows\Minidump.

CBS.log from C:\Windows\Logs\CBS — this is the key log for the failed Windows update.

If available, setupact.log and setuperr.log from C:\$WINDOWS.~BT\Sources\Panther, to investigate Setup getting stuck at 46%.

Paste each folder path into File Explorer’s address bar >> copy the files to your desktop >> zip them >> upload to OneDrive and share the link here.
Alfie 0 Reputation points

2026-11-04T16:33:27.87+00:00

You can find those here: https://drive.google.com/file/d/16QDBSd3TyJ-BOFBfVuBqpf3UuN1PTMuS/view?usp=sharing
TaoLi 119.5K Reputation points Independent Advisor

2026-11-05T13:20:54.84+00:00
Thanks for the logs. They confirm TiWorker.exe is crashing during the update, alongside SYSTEM_SERVICE_EXCEPTION and HYPERVISOR_ERROR crashes. The USB repair was cancelled before installation began.

I found a very close case with the same i9-14900KF and MSI PRO Z790-P WIFI. The owner reported that reducing the highest CPU boost ratios stopped the crashes. This makes CPU stability worth testing, although it doesn’t prove your CPU is faulty.

I’d try this before reinstalling:

Back up your files and BitLocker key >> install the latest CyberPowerPC-approved BIOS >> enable Intel Default Settings. Intel recommends microcode 0x12F or later.

If crashes continue, temporarily disable Intel Turbo Boost in BIOS and test normal use. This reduces performance and is only a diagnostic test.

If it becomes stable only with Turbo Boost disabled, share that result with CyberPowerPC for CPU/firmware assessment.

Similar case: https://community.intel.com/t/i9-14900kf-random-crashes-and-bsod-with-different-stop-codes/133010

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