File Backups Stopped Working after Windows 11 KB5083769 Undate

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I finally had some time to do some digging and Gemini suggested that sometimes vssadmin list writers hanging may not be a permanent failure with the installation of the KB, but a result of BitLocker “suspending” I/O while it waits for a protector to be validated. And suggested cycling the protectors could clear the VSS queue.

Do this by running these commands in an Elevated Command Prompt:

Disable protectors: manage-bde -protectors -disable C:

Restart the services:

net stop vss

net stop eventsystem

net start eventsystem

net start vss

Re-enable protectors: manage-bde -protectors -enable C:

Gemini said if the vssadmin list writers hang returns after a reboot it means the issue isn’t just a “stuck” protector, but a persistent policy conflict or It’s highly likely that the KB has introduced a driver-level conflict with your specific hardware/TPM firmware that a simple reset can’t bypass and one would have to resort to restarting the srevices each boot like kilrah says to do.

I went to test this theory today and re-enabled KB5083769 on the PC’s that were having the issue, installed the update and rebooted. Strange thing is none of them hang vssadmin list writers now, tried multiple reboots and backups and all backups are working nomrally. There haven’t been any new updates or even reboots since I disabled and uninstalled the KB → no idea what has changed to fix the issue.

Take what you will from this result…

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I updated another rarely used machine with bitlocker enabled yesterday as a test and it backed up successfully afterwards.

Now wondering if it’s just an install fuckup and removing/reapplying that kb is all it takes…

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From my side have introduced a timeout for this operation with the latest client version. So we should get better error messages instead of it just indexing forever. It does not fix the problem.

Acronis has a KB: Acronis Support Portal

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Here, I’ve reinstalled the April update, and seems UrBackup keep working.
Will try to reproduce if uninstall/reinstall is enough.

25

Tried it this morning, hasn’t worked for me, still need the startup script.

26

it worked only once, the next days hang occurs again.
KB5083769 re-uninstalled.

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After uninstalling KB5083769 the backup worked fine. But as you know, windows will just automatically reinstall it to the client and after having done so the forever indexing returns. We somehow need to get urbackup to run with this update installed

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Well as one may have predicted 3 of the 4 have stopped working and vssadmin list writers on those 3 is freezing. They have not been rebooted or anything.

I’ve upgraded the problem PC’s Client to V2.5.30, enabled logging, and done the procedure in my last post, rebooted, verified vssadmin list writers doesn’t hang.

I’ll give it a couple days and report back.

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Well, just to confuse things backups started working for me again. I’ve done nothing to the system since I first identified there was a problem. Very odd.

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KB5083631 is out which looks like it is doing something with Bitlocker again… Did your PC install it?

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Nope. KB5083769 is the last installed update.

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So this has blown up in the media a bit and I think we can assume Microsoft is investigating this issue.

Media is pointing at Microsoft updating this article April 14, 2026—KB5083769 (OS Builds 26200.8246 and 26100.8246) - Microsoft Support with:

[Vulnerable driver blocklist] This update introduces a security hardening change that adds known vulnerable kernel drivers to the Microsoft vulnerable driver blocklist. Backup applications that rely on blocked drivers might experience failures when attempting to mount or manage disk images.

These apps relying on blocked drivers might display error messages, including “The backup has failed because Microsoft VSS has timed out during the snapshot creation” or VSS_E_BAD_STATE. Affected users should update to a newer version of their application that uses newer drivers that include the required protections. For more information, see April 2026 Windows security updates introduce protections to known vulnerable kernel drivers.

This is confusing since UrBackup does not install drivers (if you don’t use the CBT version). What I think they are pointing at is that Macriums psmounterex.sysis blocked.

I don’t know how Microsoft draws the connection between VSS being broken and a driver not being loaded.

UrBackup is not relying on a blocked driver. It might be that people having the issue here, have software installed that has the driver blocked and that indirectly causes the backup failures. That I do not know.
If it comes to it everyone could perhaps investigate what kind of VSS writers they use, if they use this driver and it is blocked etc.? But really it is up to Microsoft to collect this kind of information to track down the bug.

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KB5083769 re-installed on 30/04/2026 + UrBackup 2.5.30
Like 6 days ago, first backup done withour errors.
Info 01/05/26 20:35 Starting scheduled incremental file backup…
Info 01/05/26 20:48 Scanning for changed hard links on volume of “C:”…
Info 01/05/26 20:48 Indexing of “Desktop” done. 2 filesystem lookups 0 db lookups and 0 db updates
[…]

No backup during week-end
Today, Timeout errors are logged (since 2.5.30),
but backup not blocked and data is here.
Info 04/05/26 20:33 Starting scheduled incremental file backup…
Errors 04/05/26 20:58 Gathering writer status failed. Timeout after 2m
Errors 04/05/26 20:58 Creating snapshot of “Desktop” failed.
[..]
Backup completed with issues

is Windows uptime (4 days) matter ?

I just installed the preview update KB5083631 build 26200.8328
Will post after some days.
(sorry for my bad english wording)

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Just to definitely rule out that this is not caused by the fix of CVE-2023-43896, could everyone please confirm or deny that they have Macrium Reflect installed on the clients

  • Macrium Reflect is installed
  • Macrium Reflect is not installed
0 voters
35

So the backups stopped working, again. Came across a couple of items. My Windows 11 backup broke after KB5083769 — Microsoft says this simple fix might save your files | Windows Central

A pretty clear explanation of what seems to be going on. According to Microsoft…
“Since this problem is not a bug in the April update, Microsoft recommends simply updating to the latest version of the backup solution that uses the newer drivers.”

Sounds like it’s going to be up to the backup vendors to fix this.

I did come across a registry hack that is supposed to enable the backups to run.

https://www.neowin.net/news/registry-hack-lets-you-bypass-windows-11-kb5083769-kb5083631-patch-that-blocks-some-apps/

I thought this is a better alternative then backing out KB5083769. I tried it and it worked today. I’ll report more results again in a couple of days.

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I wrote about this here:

I don’t know why the media has adopted the Microsoft narrative even though it is obviously not true. The poll above shows that none of the people in this thread having the issue have the mentioned driver installed.

There is nothing from the UrBackup side that can fix this.

You probably didn’t have a blocked driver installed either. The issue seems to only occur randomly, so at the moment it probably just randomly does not occur. Nothing to do with what you did in the registry.

1 Like
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Not sure if this is helpful to others but I appear to have fixed my urbackup failing after the KB5083769 update.

I noticed that:
vssadmin list shadowstorage

Was returning that my C: drive had a maximum of 10GiB of storage set.
This is unusual from what I can tell because its normally roughly 10% of the drive storage - 160GiB in my case.

Resetting this via:
vssadmin Resize ShadowStorage /For=c: /On=c: /Maxsize=10%

Now means I have completed two succesful backups without incident.

I did not change this myself, didn’t even know the commands to do so. It came up whilst trying to find solutons to the problem of backups failing. I also don’t know what it was set to prior to the update or if the update changed it. I only know it was set to 10GiB (which based on current backup cycles was not large enough) and it now works.

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Update to my previous post. The registry hack did not work. Backups failed the next day. The command vssadmin list writers hangs.

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I checked all my PC’s for the Event ID 3077 error → none. Tried the VulnerableDriverBlocklistEnable registry change → still fails after couple days. Changed it back for security reasons…

Checked the shadow storage max size and mine were also set to 10G (less than 1% of C). Changed to 10%, rebooted. Guess we will see in a couple days. I’ll report back

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Mine is still working fine now after the 10% resize. Several days and backups later.
Fingers crossed yours does as well.