Why Your Backups Suddenly Started Failing
If you have seen a Windows update backup failure over the last few weeks, you are not alone. Microsoft’s April cumulative update KB5083769 added a shared kernel driver, psmounterex.sys, to the Vulnerable Driver Blocklist to plug a high‑severity buffer overflow tracked as CVE-2023-43896. That driver sits at the heart of disk-image mounting in several popular products, including Macrium Reflect, Acronis Cyber Protect Cloud, UrBackup Server, and NinjaOne Backup. When Windows now refuses to load psmounterex.sys, image creation may appear to succeed, but image-mount and some snapshot operations can fail, stall, or time out. Symptoms often resemble generic Volume Shadow Copy Service (VSS) problems, such as VSS snapshot timeouts or VSS_E_BAD_STATE errors, which can easily be misdiagnosed as routine software glitches instead of a deliberate security block introduced by KB5083769.
How KB5083769 Impacts Macrium, Acronis, and Other Backup Tools
The KB5083769 Macrium Acronis issue is not caused by a bug in the backup tools themselves, but by Windows blocking a vulnerable driver they all share. Psmounterex.sys is used to mount and manage disk images; once it lands on Microsoft’s Vulnerable Driver Blocklist, Windows 10, Windows 11, and Windows Server will no longer load it under App Control for Business policies. The result is backup software compatibility problems across multiple vendors at once. Jobs that rely on image-mount or snapshot functionality may fail to start or complete, while basic image creation might still appear normal. Administrators can confirm the true cause by opening Event Viewer and checking the Code Integrity log for Event ID 3077 tied to policy ID {D2BDA982-CCF6-4344-AC5B-0B44427B6816}, which records that psmounterex.sys was blocked. This log entry is the clearest indicator that the Windows update—rather than the backup application—is behind the failure.
Dell SupportAssist BSOD Crashes and Reboot Loops
At the same time, many Dell users are fighting a different but equally disruptive problem: nonstop blue screens. Dell’s SupportAssist Remediation version 5.5.16.0, released on April 30, is triggering CRITICAL_PROCESS_DIED stop errors roughly every 30 minutes on affected systems, including XPS 15 9530, Precision 3571, and Dell Pro Plus 14 models. Instead of quietly protecting your system, DellSupportAssistRemediationService.exe is driving machines into BSOD and reboot loops, killing work sessions and creating the impression of a broader Windows instability. Community members armed with debugging tools such as WinDbg traced crash dumps back to the remediation service, and many report that removing or disabling this single component immediately restores stability. Because these crashes can occur during active backup jobs, they compound the risk from existing Windows update backup failure issues, potentially leaving users both unstable and unprotected.
Immediate Safety Steps: What to Disable, What to Keep
For now, your top priority is stability and recoverability, not feature completeness. If you are experiencing BSODs or reboots on a Dell system, disable the "Dell SupportAssist Remediation" service immediately, or uninstall SupportAssist Remediation and the OS Recovery Plugin through Control Panel. This stops Dell-related crashes without affecting core Windows updates. For backup failures tied to KB5083769, do not uninstall the security update; it closes a serious kernel-level hole that attackers could exploit. Instead, temporarily avoid image-mount operations that rely on the blocked driver and verify that recent backup jobs have actually completed and passed integrity checks. If you run scheduled backups on production systems, consider adding extra manual restore tests from existing images, so you are not assuming protection from jobs that may be silently failing or producing unusable snapshots.
Long-Term Fixes and How to Stay Ahead of Breakages
Both problems have clearer long-term paths than it might seem. On the Windows side, Microsoft has indicated it will not remove psmounterex.sys from the Vulnerable Driver Blocklist because the underlying vulnerability is too serious. Instead, backup vendors are preparing new builds that replace psmounterex.sys with a hardened, non-blocklisted driver. The real fix is to update Macrium, Acronis, UrBackup, NinjaOne, and similar tools as soon as their patched versions ship. For Dell systems, keep an eye on SupportAssist Remediation release notes and only reinstall once Dell has acknowledged and fixed the BSOD behaviour. More broadly, treat any sudden Windows update backup failure or unexpected Dell SupportAssist BSOD as a potential compatibility issue: pause automation, verify backups and restore tests, review system logs, and check with vendors before making drastic changes like rolling back critical security patches.