Windows 11 KB5083769 update breaks third-party backup tools via VSS timeout

Microsoft’s April 2026 KB5083769 security update is breaking backup software on Windows 11 24H2 and 25H2 by causing Volume Shadow Copy Service snapshots to time out. The failure surfaces across multiple vendors that depend on VSS for consistent point-in-time backups, including Acronis Cyber Protect Cloud, Macrium Reflect, NinjaOne Backup, and UrBackup Server. Acronis has confirmed the impact on both Pro and Home editions and noted that affected machines can also drop their connection to its cloud console and appear offline.

VSS is a foundational Windows component that coordinates the OS, backup agents, and transactional applications like SQL Server and Exchange to produce consistent snapshots. A timeout at that layer cascades into total backup-job failure with the message indicating VSS timed out during snapshot creation. Until Microsoft ships a fix, the only workaround is uninstalling KB5083769 via Windows Update history and pausing further updates to prevent reinstallation.

The regression follows a rough patch cycle: Microsoft already shipped out-of-band fixes this month for Windows Server restart loops triggered by the April security rollup, and warned that some Windows Server 2025 systems boot into BitLocker recovery after installing KB5082063. The pattern points to insufficient pre-release validation of storage and boot-path interactions in the April train.