Microsoft 365 Alert – Service Degradation – Microsoft Defender XDR – Admins may notice excessive memory usage on their Windows Server 2016 machines – ONGOING

01/04/2026 09:22:00 AM

NHSmail Reference: INC46787846

Microsoft Reference: DZ1266872

Issue Status: RESOLVED

Issue Description: Admins may notice excessive memory usage on their Windows Server 2016 machines.

More info: Admins may notice delays or timeouts with third-party applications hosted on affected Windows Sever 2016 machines running Microsoft Defender for Endpoint’s Sense.

Final Update: 14/04/2026 08:40:00 AM– Microsoft has determined that a recent code change exposed an issue with how the Windows Server 2016 machine operating system handles Microsoft Defender for Endpoint service requests and was resulting in the observed impact. We’ve confirmed through an extended period of monitoring that our service optimizations have successfully reached all previously impacted devices, fully resolving the issue.

Scope of impact: Any Windows Server 2016 admin may be affected.

Root cause:  A recent code change exposed an issue with how the Windows Server 2016 machine operating system handles Microsoft Defender for Endpoint service requests, which resulted in impact

Next steps by: Microsoft are reviewing our code change check and implementation processes to improve how we detect potential operating system issues and prevent similar service incidents in the future