Winsage
October 16, 2025
Microsoft's security updates have caused synchronization failures in Active Directory environments on Windows Server 2025, acknowledged on October 14, 2025. The issue stems from the September 2025 security update KB5065426, affecting applications like Microsoft Entra Connect Sync, which struggle to replicate AD security groups with over 10,000 members. This problem leads to incomplete synchronization, particularly impacting large enterprises in sectors like finance and healthcare, resulting in access denials and compliance risks. A registry tweak can temporarily disable the problematic feature, but Microsoft warns of potential risks in modifying the registry. The company is investigating the issue and plans to release a fix in a future update, with client platforms remaining unaffected. IT teams are advised to monitor updates and test changes in staging environments before applying them in production.