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Microsoft Acknowledges Windows Server 2025 Sync Bug, Promises Fix

10/16/2025

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Summary

Story summary

Microsoft confirms a Windows Server 2025 sync bug introduced by the September 2025 security update KB5065426, disrupting DirSync for large groups (over 10,000 members) and causing incomplete syncs.
A temporary registry workaround is available, but incorrect edits could cause system instability.
Microsoft is investigating and plans a permanent fix in a future update.
IT administrators should monitor sync activity and avoid applying updates until a patch is released.

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Story summary

Microsoft confirms a Windows Server 2025 sync bug introduced by the September 2025 security update KB5065426, disrupting DirSync for large groups (over 10,000 members) and causing incomplete syncs.
A temporary registry workaround is available, but incorrect edits could cause system instability.
Microsoft is investigating and plans a permanent fix in a future update.
IT administrators should monitor sync activity and avoid applying updates until a patch is released.