driver blocklist Archives

Winsage

May 10, 2026

Microsoft Confirms KB5083769 Breaks Macrium and Acronis Backups

Microsoft's April 2026 Windows security update, KB5083769, may disrupt image-mount operations for backup applications such as Macrium Reflect, Acronis Cyber Protect Cloud, UrBackup Server, and NinjaOne Backup due to the addition of the psmounterex.sys kernel driver to its Vulnerable Driver Blocklist. This action was taken to address a high-severity buffer overflow vulnerability, CVE-2023-43896. The inclusion of this driver in the blocklist has rendered several backup products inoperable, and Microsoft will not retract the block for security reasons. Administrators can use Event ID 3077 in the Code Integrity log to confirm that the blocklist is causing the failures. Microsoft advises updating backup applications to versions that include necessary driver protections instead of uninstalling or pausing the security patch. Additionally, the April updates have caused other issues, such as failures in Windows Server installations and devices booting into BitLocker recovery mode.

Winsage

May 8, 2026

Windows update is breaking backups, and here’s how you can fix it

A recent Windows update, KB5083769, released on April 14, 2026, blocks the psmounterex.sys driver, disrupting the functionality of third-party backup software like Acronis Cyber Protect Cloud, Macrium Reflect, and NinjaOne. This driver is essential for loading and mounting backup storage images. Users may encounter errors related to Microsoft VSS during backup attempts. The update is a security enhancement, not a bug, and users are advised to upgrade their backup software to versions that use a newer driver or temporarily uninstall the KB5083769 update. It is recommended to check for updates from the backup software provider and pause Windows Updates to prevent automatic reinstallation of the problematic update until a fix is available.

Winsage

May 5, 2026

April 2026 Windows Update Breaks Third-Party Backup Software by Blocking Vulnerable Driver

Microsoft will include the psmounterex.sys driver in its Vulnerable Driver Blocklist in the April 2026 security update, affecting third-party backup applications that use this driver for image mounting and Volume Shadow Copy Service (VSS) snapshots. This decision addresses CVE-2023-43896, a critical buffer overflow vulnerability. Affected software includes Macrium Reflect, Acronis Cyber Protect Cloud, UrBackup Server, and NinjaOne Backup on Windows 11, Windows 10, and Windows Server platforms. Users may face issues during image-mount operations, receiving error messages related to VSS timeouts and Code Integrity errors in the Event Viewer. To check if a system is affected, users can look for Event ID 3077 in the Code Integrity Operational log. Microsoft recommends upgrading to newer versions of backup applications that do not use blocked drivers and advises against uninstalling or delaying the April update. Additionally, the update may cause certain Windows Server 2025 devices to boot into BitLocker recovery mode and has led to out-of-band updates for Windows Server update failures and restart loops on domain controllers.