Microsoft's April 2026 KB5083769 security update for Windows 11 (versions 24H2 and 25H2) breaks third-party backup software across multiple vendors. The patch introduces a compatibility issue that prevents backup applications from functioning correctly, leaving systems unable to complete scheduled backups.
Defenders using third-party backup tools should delay patching until vendors release compatibility updates. Microsoft has not yet issued a revised patch or provided workaround documentation. Affected vendors have begun investigating root causes, with initial reports pointing to changes in file system APIs or filter driver behavior introduced by the security update.
Organizations should inventory backup software deployments before rolling out KB5083769. Test the patch in non-production environments first. Contact backup vendors directly for updated versions or temporary mitigations. Prioritize systems requiring the security update against backup continuity needs. Microsoft typically publishes details within its security update documentation. Check vendor websites for compatibility notices and revised releases.
This represents a common tension between security patching cadence and application stability. Stagger deployment across your environment rather than broad simultaneous rollout.