Important: Windows KB5083769 update may cause backups to get stuck

[Imperator Ten]

I have seen some post about " psmounterex.sys " and whether Microsoft know what the problem is.
I think the issue is not about only  " psmounterex.sys ", but about vulnerable driver, in general.
So Backup SW needs to determine if their driver are vulnerable or not.  

 Well here are my thoughts.
The Microsoft article was about (mostly) the problem with Macrium backup. But we know that the patch has caused other Backup SW to fail. HBS and Acronis to name a couple. I do not think that Acronis would be using  a driver ( psmounterex.sys ) own and controlled by Macrium,  HBS can tell us if they do, but I am betting they do not.
So, in MS article replace  " psmounterex.sys " with "vulnerable driver" 

This is what I take away from the Microsoft:
From MS:
       ->These Windows updates include routine security hardening to help protect devices by blocking third-party drivers with known vulnerabilities.

So  " psmounterex.sys " is one of these driver, but not necessarily the only one. So if the Backup SW driver have known vulnerabilities, it is or will be on the  Microsoft vulnerable driver blocklist.  Not sure how Microsoft determines if a driver is vulnerable or not, if anyone knows, please help us understand


I think what was clear from Microsoft, for this instance, is that MS are NOT fixing it.
From MS:

• This intentional change of behavior is designed to protect devices against known vulnerabilities in the psmounterex.sys kernel driver. Following the installation of Windows updates released on or after April 14, 2026, Windows Code Integrity enforcement will block vulnerable versions of this driver from loading when the Microsoft vulnerable driver blocklist is enabled.
  
• The psmounterex.sys driver will remain on the Microsoft vulnerable driver blocklist. Applications that depend on this driver will continue to experience failures until they are updated to a newer version that includes the required protections.
  

I think what was clear from Microsoft, for this instance, is that MS are NOT fixing it.

If anyone have found an Article where MS talks about another problem with backup, after the April, please provide a link.

[MDisney]

Using 5.8.2.0 I experienced backup freeze on three separate computers. I tried solution at below website and problems have gone away.

Go to elevenforum website and search on post 734708 (for some reason I cannot post a link in this message)

[admin]

Dear all,

It seems we made a mistake in version 260506, please try this temporary version:
https://www.easyuefi.com/backup-software...260507.exe

Best regards,

[YasarYY]

Tests with the 260507 version:
I couldn't wait for system backups to complete b/c of limited time I have, but they are probably ok as they start & cancel.

* Core isolation features: off
System backup: starts (cancelable)
Disk/Partition backup: starts & completes
File backup: stuck at "calculating the total size of the files..." [1]

* Core isolation features: on
System backup: starts (cancelable)
Disk/Partition backup: starts & completes
File backup: stuck at "calculating the total size of the files..." [1]

[1]: log: 127 (Waiting for the asynchronous operation to finish...)

[admin]

Tests with the 260507 version:
I couldn't wait for system backups to complete b/c of limited time I have, but they are probably ok as they start & cancel.

* Core isolation features: off
System backup: starts (cancelable)
Disk/Partition backup: starts & completes
File backup: stuck at "calculating the total size of the files..." [1]

* Core isolation features: on
System backup: starts (cancelable)
Disk/Partition backup: starts & completes
File backup: stuck at "calculating the total size of the files..." [1]

[1]: log: 127 (Waiting for the asynchronous operation to finish...)

The backup you created seems to be a file backup rather than a system backup. A real system backup task does not calculate the size of the files to be backed up. Please provide the log files to us so that we can analyze whether the changes have taken effect.


Thanks.

[YasarYY]

There may be a misunderstanding. Stuck at "calculating the total size of the files..." message only happens at file backups, not at system or Disk/Partition backups.

[admin]

I have seen some post about " psmounterex.sys " and whether Microsoft know what the problem is.
I think the issue is not about only  " psmounterex.sys ", but about vulnerable driver, in general.
So Backup SW needs to determine if their driver are vulnerable or not.  

 Well here are my thoughts.
The Microsoft article was about (mostly) the problem with Macrium backup. But we know that the patch has caused other Backup SW to fail. HBS and Acronis to name a couple. I do not think that Acronis would be using  a driver ( psmounterex.sys ) own and controlled by Macrium,  HBS can tell us if they do, but I am betting they do not.
So, in MS article replace  " psmounterex.sys " with "vulnerable driver" 

This is what I take away from the Microsoft:
From MS:
       ->These Windows updates include routine security hardening to help protect devices by blocking third-party drivers with known vulnerabilities.

So  " psmounterex.sys " is one of these driver, but not necessarily the only one. So if the Backup SW driver have known vulnerabilities, it is or will be on the  Microsoft vulnerable driver blocklist.  Not sure how Microsoft determines if a driver is vulnerable or not, if anyone knows, please help us understand


I think what was clear from Microsoft, for this instance, is that MS are NOT fixing it.
From MS:

• This intentional change of behavior is designed to protect devices against known vulnerabilities in the psmounterex.sys kernel driver. Following the installation of Windows updates released on or after April 14, 2026, Windows Code Integrity enforcement will block vulnerable versions of this driver from loading when the Microsoft vulnerable driver blocklist is enabled.
  
• The psmounterex.sys driver will remain on the Microsoft vulnerable driver blocklist. Applications that depend on this driver will continue to experience failures until they are updated to a newer version that includes the required protections.
  

I think what was clear from Microsoft, for this instance, is that MS are NOT fixing it.

If anyone have found an Article where MS talks about another problem with backup, after the April, please provide a link.

The psmounterex.sys file is a proprietary driver of Macrium. Neither Hasleo nor any other backup software uses it.

If the issue were truly caused by the "vulnerable driver blocklist", then technically, simply disabling that blocklist should restore normal backup functionality. However, that does not seem to be the case.

Moreover, judging by its name, psmounterex.sys is merely a driver for mounting backup images (unless Macrium itself mounts an image during the backup process). In principle, it should not cause the backup operation itself to fail. This is precisely where Microsoft's explanation falls short.

Does Microsoft have a plan to kill off all third-party backup software and monopolize the market, just as they did with other software in the past? However, the backup market is simply too small for a giant like Microsoft.

[Bespoken]

Dear all,

It seems we made a mistake in version 260506, please try this temporary version:
https://www.easyuefi.com/backup-software...260507.exe

Best regards,

System and Partition backups still work, and File backups still freeze at the calculating stage.

Let me know if I can provide any more details or assistance.

[Imperator Ten]

Hi all
Tested Hasleo_Backup_Suite_Free_260507.exe
Mix results: File backup Completes first time it runs after restart, but then fails after that, until next restart.

Installed Hasleo_Backup_Suite_Free_260507.exe
Restarted Computer
File Backup Full: completed.
Saved Games to ensure there was new file.
File Backup incremental: Hung -> 0%
Restarted Computer
File Backup incremental: completed.
Saved Games to ensure there was new file.
File Backup incremental: Hung -> 0%
Power off/on computer ooops, meant to do restart.
File Backup incremental: completed.
waited a bit
File Backup incremental: Hung -> 0%
***************************

Core Isolation: All on.
Other Observations.
I clear all of my events log before running the test. 
After the attempted backup, there was no Errors, or warning. 
Also, no CodeIntegrity Events. ( I concede, this is not a Vulnerable Driver problem. )

[JayDee]

Tested Hasleo_Backup_Suite_Free_260507.exe
Sort of works for file backups.
If I create a new backup job it worked
Trying to run previously created jobs still seems to hang
Not every new job worked... have not identified the differences yet

BTW Cancel now typically works except for the failing previous job.
For that, I still needed Task Manager

Is it related in any way to the size of the backup?
On one test I created a job rather small
it worked
add to it
it worked
and so on
ultimately it failed

Still testing...
JayDee