Microsoft confirmed that Windows security updates released on or after April 14, 2026, including KB5083769, can break disk-image mounting and related restore workflows in Macrium Reflect, Acronis Cyber Protect Cloud, UrBackup Server, and NinjaOne Backup by blocking psmounterex.sys. The company...
Microsoft’s April 14, 2026 Windows 11 security update KB5083769 deliberately blocks vulnerable versions of the psmounterex.sys kernel driver, causing some third-party backup tools on Windows 11, Windows 10, and Windows Server to fail when mounting or managing backup images. The immediate fix is...