Important: Windows KB5083769 update may cause backups to get stuck

[admin]

Dear all,

Thank you, @lavande, for sharing this information.

Here is Microsoft's original article:
https://support.microsoft.com/en-us/topi...3c1b1aa9d0

April 2026 Windows security updates introduce protections to known vulnerable ke…
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psmounterex.sys is a driver specific to Macrium Reflect, Hasleo and other backup software do not use it. Such a driver, used only for mounting images, has been turned by Microsoft into the trigger for VSS backup failures, it's really baffling. Does Microsoft actually understand the root cause of the VSS issue?

So, perhaps we should first find out: are all the affected computers installed with Macrium Reflect? And will uninstalling Macrium Reflect resolve the problem?

Best regards,

[YasarYY]

Hi,
Same issue here (had worked last month), system and disk/partition backup stuck at %0 (waited for max 50 mins), HasleoBackupSuiteService is running, canceling doesn't work, have to kill processes, no cpu/disk usage at task manager.
I have version 5.8.2.0 (win11 and KB5083769).
I had Macrium Reflect once, but have uninstalled it about 3-4 months ago, I don't think any remains are left.
Tried tools -> repair VSS, got "the operation completed successfully" message within several seconds, but no change at stuck behavior.
backing up 1 or more non-system partition works.
backing up the system partition doesn't work.
FWIW, at BackupWorker.log, last line (before process kill) is:
2026-05-04 10:47:29 T:000034B8 127 (Waiting for the asynchronous operation to finish...)
At Event Viewer (CodeIntegrity\Operational), I don't have any "Event ID 3077" (a driver is being blocked by the Microsoft vulnerable driver blocklist).

[admin]

Hi,
Same issue here (had worked last month), system and disk/partition backup stuck at %0 (waited for max 50 mins), HasleoBackupSuiteService is running, canceling doesn't work, have to kill processes, no cpu/disk usage at task manager.
I have version 5.8.2.0 (win11 and KB5083769).
I had Macrium Reflect once, but have uninstalled it about 3-4 months ago, I don't think any remains are left.
Tried tools -> repair VSS, got "the operation completed successfully" message within several seconds, but no change at stuck behavior.
backing up 1 or more non-system partition works.
backing up the system partition doesn't work.
FWIW, at BackupWorker.log, last line (before process kill) is:
2026-05-04 10:47:29 T:000034B8 127 (Waiting for the asynchronous operation to finish...)
At Event Viewer (CodeIntegrity\Operational), I don't have any "Event ID 3077" (a driver is being blocked by the Microsoft vulnerable driver blocklist).

Based on your description, this issue does not appear to be directly caused by psmounterex.sys. However, to completely rule out the possibility, could you please check whether the psmounterex.sys file still exists in the C:\Windows\System32\drivers directory? Thanks.

[YasarYY]

Nope, I don't have psmounterex.sys in C:\Windows\System32\drivers directory, or anywhere in C:\Windows\System32.

[Bespoken]

psmounterex.sys impact the "image mount" function only. It has no impact to the backup process. There is a workaround to decrease security to allow it to run.

There are other activities that result in the VSS failure, and at least one of these is PC specific. If you do not get the failure then you do not have one of these PC. My daily driver is one of the affected PC's, and both MR8.1 and HSB are affected. I have even done a fresh install of Win 11 and the problem persists.

In preparation for an HSB backup VSS is reset, PC rebooted, then the backup is started. It will run then stops at 79% but the image is actually successfully created..

[Froggie]

A BATCH Script is available HERE in ElevenForums that seems to address the VSS problem following the installation of KB5083769.

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[JayDee]

Tried the script but it didn't solve the problem (for me)

JayDee

[Bespoken]

That batch script was my post. It should temporarily fix the VSS proble, a restart may be required, allowing the back to run. See other comments here.

[lavande]

Microsoft probably doesn't know the origin of the VSS problem. A few months ago, Microsoft committed to fixing Windows 11 bugs by 2026 and releasing fewer new features. There have been many articles about this online.

Today I made two system backups on two computers, and I didn't have any problems. I've never installed Macrium Reflect. Both computers have Smart App Control disabled. They have The Vulnerable Driver Blocklist enabled. Both have the latest stable build of Windows 11. I have version 5.8.2.0 of HBS.

[garioch7]

@lavande,

Some of us have MR8.1 (with the infamous vulnerable driver) and HBS.  My imaging has been error-free with HBS.  This appears to only affect a limited number of computers.

The real issue is what is really causing issues for VSS with some computers ... ?

Have a great day.

Regards,
Phil