Are you using Windows 11 versions 24H2 or 25H2? If so, you might want to not download April’s KB5083769 cumulative security update after multiple reports of third-party backup applications breaking following installation. At the time of writing, the backup vendors known to be impacted by this security update failure include Acronis, Macrium, NinjaOne and UrBackup. Here’s what we know so far and the mitigation steps to take until Microsoft resolves the issue.

Microsoft Windows 11 KB5083769 Security Update Breaks Some Backup Applications

While it is always good practise to install security updates as soon as possible , sometimes there are unforeseen consequences. Unfortunately, Microsoft has something of a track record in the update failure stakes, from disappearing passwords to broken VPN connections . The latest security update issue stems from the installation of the April cumulative Windows 11 security update, reference KB5083769, which has now been reported as causing backup applications from multiple vendors to fail due to a service timeout issue.

The broken backups issue first came to light on April 29, when it was reported that the Windows 11 24H2 and 25H2 April update was causing problems for users across support forums, official and otherwise. Although, at the time of publication, the official Microsoft support pages for KB5083769 shows no details of known issues with backups, the problem is thought to sit with the Volume Shadow Copy Service. Software using these VSS snapshots are seemingly experiencing a service timeout which, in turn, cause the backups to fail.

While the default Windows cloud backups are working normally, third-party apps are being impacted. An official Acronis advisory , for example, stated that this affects users of the Cyber Protect console on both Windows 11 Home and Windows 11 Pro editions. “This update may introduce system-wide issues that affect Microsoft VSS (Volume Shadow Copy Service) operations, leading to backup failures,” Acronis confirmed.

I have reached out to Microsoft for a statement and will update this article as soon as I have anything further to report. However, in the meantime, if your backups are failing then seek support from your vendor in the first instance to determine if the cause is likely to be the Windows 11 security update. If it is, then Acronis has advised users, by way of a temporary workaround, to uninstall the KB5083769 update and reboot the machine. “After removing the update and restarting the system,” Acronis said, “backup operations should resume successfully without requiring any changes to Microsoft VSS or the Acronis agent.”