Microsoft ran into trouble with its September updates for Windows Server 2025. The company confirmed that these updates are causing major headaches for businesses trying to keep their computer systems in sync. The problems specifically affect something called Active Directory, which is basically how companies manage who has access to what on their networks.
The issue showed up after companies installed the September 2025 security update. Microsoft released this update to fix security holes and keep systems safe from hackers. But instead of making things better, the update broke an important feature that helps companies keep their user information synchronized between different systems.
Many businesses use Active Directory to manage employee accounts, passwords, and permissions. When someone joins the company, IT departments add them to various groups that determine what files and programs they can access. Some of these groups are huge, with more than 10,000 people in them. After installing the September update, these large groups stopped syncing properly.
The problem gets worse for companies that use cloud services alongside their regular computer systems. Many businesses now have some stuff stored on their own servers and other stuff in Microsoft’s cloud. They use tools to keep everything in sync so employees can access what they need regardless of where it’s stored. The September update broke this syncing process for big groups.
Microsoft officially acknowledged the problem on October 14, 2025. The company explained that applications relying on directory synchronization would see incomplete results when dealing with security groups larger than 10,000 members. This means that some employees might suddenly lose access to files or programs they need for work, or worse, some people might get access to things they shouldn’t see.
The September update that caused all this trouble goes by the name KB5065426. Anyone who installed this update or any newer ones released in October faced the same problems. That’s a lot of companies considering how many businesses run Windows Server 2025 for their operations.
What makes this situation particularly frustrating is that the update was supposed to improve security. Companies install these updates to protect themselves from threats and keep their networks safe. Nobody expects a security update to break basic functions that businesses depend on every day. Yet that’s exactly what happened here.
For IT departments managing these systems, the timing couldn’t be worse. Many companies had already rolled out the September updates to their servers before anyone realized there was a problem. By the time Microsoft confirmed the issue in mid-October, the damage was done. IT teams suddenly found themselves dealing with synchronization failures and confused employees who couldn’t access their usual resources.
Microsoft offered a temporary fix while they worked on a proper solution. The workaround involves changing something in the Windows registry, which is like the control panel for advanced system settings. IT administrators can disable the feature that’s causing problems by creating a specific registry entry. However, Microsoft warns that messing with the registry is risky business. One wrong move could cause serious system problems that might require completely reinstalling the operating system.
The registry fix requires going to a specific location in the system settings and creating a new value with a very specific name and number. IT professionals comfortable with registry editing can do this, but it’s definitely not something regular users should attempt. Microsoft stressed that people should back up their systems before making any registry changes just in case something goes wrong.
Even with the workaround available, many IT departments hesitate to use it. Editing the registry always carries risks, and doing it across multiple servers in a company network multiplies those risks. Some businesses decided to wait for Microsoft’s official fix rather than potentially create new problems trying to solve the current one.
The good news is that only Windows Server 2025 is affected. Companies still running older versions like Windows Server 2022 don’t have this particular problem. But that’s cold comfort for organizations that upgraded to the newest version expecting improvements and better features. Instead, they got broken functionality and extra work for their IT teams.
This situation highlights a bigger issue with software updates. Companies face a constant dilemma – install updates quickly to stay protected against security threats, or wait to see if updates cause problems. Those who install updates immediately sometimes become unpaid testers who discover bugs the hard way. Those who wait might leave themselves vulnerable to attacks that the updates were meant to prevent.
Microsoft says their engineers are actively working on a permanent fix. The company hasn’t given a timeline for when that fix will arrive, only promising it will come in a future update. For businesses dealing with synchronization problems right now, that’s not very reassuring. They need solutions today, not promises about eventual fixes.
The problem also affects Microsoft’s own cloud service, formerly known as Azure Active Directory and now called Microsoft Entra ID. Companies using this service to connect their on-premises systems with cloud resources found that the September update disrupted these connections. Since many businesses have moved to hybrid setups with both local and cloud components, this affects a significant number of organizations.
In the meantime, system administrators are left weighing their options. They can apply the registry workaround and hope nothing breaks. They can remove the September update and potentially leave their systems exposed to security vulnerabilities. Or they can wait for Microsoft’s official fix while dealing with synchronization problems and frustrated users.
This incident adds to a growing list of problematic Windows updates in recent years. Microsoft has faced criticism before for releasing updates that caused more problems than they solved. Each time this happens, it erodes trust in the update process and makes IT departments more cautious about installing new patches.
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