Overview
- Microsoft said the April Windows update can disrupt some third‑party backup tools by stopping a driver those tools use for recovery tasks.
- The change targets psmounterex.sys, which Windows now treats as unsafe after a kernel flaw was identified as CVE-2023-43896.
- Many users can still create full images, but attempts to mount or restore those backups fail with errors on Windows 11, Windows 10, and Windows Server.
- Vendors reported issues in products such as Acronis Cyber Protect Cloud, Macrium Reflect, NinjaOne Backup, and UrBackup Server.
- Microsoft advises keeping the security update installed and moving to backup software with newer, secured drivers, while some reports note uninstalling the update restores function but reopens the vulnerability.