Microsoft Confirms Windows Server 2016 Bug After KB5087537 Update

Microsoft has confirmed a new issue affecting systems running Windows Server 2016 after the May 2026 security updates.

The problem appears after installing the KB5087537 update and can prevent affected servers from locating domain controllers correctly. Microsoft says the issue only affects systems using hostnames that are exactly 15 characters long.

Domain controller discovery can fail

According to Microsoft, affected systems may fail DCLocator requests and return ERROR_INVALID_PARAMETER during domain controller discovery operations.

One example Microsoft provided is:

nltest /dsgetdc:<domain> /pdc

The issue can stop applications, scripts, and administrative tools from finding an available domain controller.

Only specific hostname lengths appear affected

Microsoft says the bug currently affects Windows Server 2016 devices with hostnames containing exactly 15 characters.

The company did not mention shorter or longer hostnames as affected by the issue.

That makes the bug unusually specific, but it could still impact enterprise environments where naming policies use fixed-length hostnames across server deployments.

Administrative tools may stop working

Microsoft warned that tools and services relying on domain controller discovery can fail on affected systems.

One example specifically mentioned by the company is DFS Namespace management, which may stop functioning correctly when the server cannot complete domain controller lookup requests.

Admins could also see failures in automation tasks, scripts, or applications that depend on Active Directory discovery mechanisms.

No fix timeline yet

Microsoft says it is currently investigating the issue. The company has not announced a workaround or estimated timeline for a permanent fix.

The problem arrives during a busy time for Windows Server administrators. Microsoft recently released emergency updates to fix Windows Server crashes, while Windows Server 2025 feature upgrades also started rolling out through Windows Update.

Via BleepingComputer