Microsoft has confirmed a bug in recent Defender updates that can incorrectly warn you that Microsoft Defender Antivirus is turned off even when the security software is still active and working normally.
The issue affects several versions of Windows 10, Windows 11, and Windows Server. Microsoft says the warning can appear when Windows starts and may continue showing up intermittently afterward, even if Defender settings correctly show that antivirus protection is enabled.
The company is working on a fix that will arrive through a future Microsoft Defender Antivirus update, although no release date has been announced yet.
The Warning Does Not Mean Defender Is Actually Disabled
The most important point is that the notification itself is incorrect.
Affected PCs can display a message saying Microsoft Defender Antivirus has been turned off, but the antivirus engine can continue running normally in the background.
Microsoft says the bug was introduced by recent Defender updates rather than by a broader Windows security failure.
| Detail | Information |
|---|---|
| Problem | False Defender disabled warning |
| Actual antivirus status | Defender can still be active |
| Windows 11 affected | 26H1, 25H2, 24H2, 23H2 |
| Windows 10 affected | 22H2, 21H2, Enterprise LTSC 2019, Enterprise LTSC 2016 |
| Windows Server affected | 2025, 2022, 2019, 2016, 2012 R2, 2012 |
| Fix status | In development |
| Fix delivery | Future Defender update |
| Release date | Not announced |
The warning can also continue appearing even if notification settings are disabled, which makes the problem more confusing.
If you see the message, checking Windows Security is more useful than assuming protection has stopped. If Defender still shows as active and its settings are enabled, the notification may simply be the result of this known bug.
Several Windows Versions Are Affected
The problem is not limited to one Windows 11 release.
Microsoft says the bug affects Windows 11 versions 26H1, 25H2, 24H2, and 23H2.
Windows 10 systems are also affected, including versions 22H2 and 21H2, as well as Enterprise LTSC 2019 and Enterprise LTSC 2016.
Windows Server installations are part of the affected group too, including Server 2025, 2022, 2019, 2016, 2012 R2, and 2012.
That broad range suggests the issue is tied more closely to Defender itself than to one specific Windows version.
Microsoft Is Preparing a Fix
Microsoft has acknowledged the problem and says a resolution will be delivered through a future Defender Antivirus update.
There is currently no confirmed release date.
That means affected systems may continue showing the incorrect warning until the next Defender update containing the fix becomes available.
For now, the key point is that the warning does not automatically mean your antivirus protection has stopped working.
If Defender settings continue showing that protection is active, the message may simply be the known notification bug rather than an actual security problem.
The issue is annoying because antivirus warnings are designed to demand attention, but Microsoft has confirmed that this particular message can be false. Until the fix arrives, checking Defender’s real status inside Windows Security is the best way to distinguish the bug from a genuine protection problem.
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