Windows defender crash on scan

Question

Windows defender crash on scan

Xander Warren 50

I get this every time I quick scan as of august 18th. Here is the xml file. Anyone else getting this? It was fine yesterday and now it's not.
Edit I posted the wrong event :p

<Event xmlns="__http://schemas.microsoft.com/win/2004/08/events/event__">
<System> <Provider Name="Application Error" Guid="{a0e9b465-b939-57d7-b27d-95d8e925ff57}" /> <EventID>1000</EventID> <Version>0</Version> <Level>2</Level> <Task>100</Task> <Opcode>0</Opcode> <Keywords>0x8000000000000000</Keywords> <TimeCreated SystemTime="2026-08-18T21:43:35.7211200Z" /> <EventRecordID>22827</EventRecordID> <Correlation /> <Execution ProcessID="18404" ThreadID="8812" /> <Channel>Application</Channel> <Computer>DESKTOP-Q2OUQJN</Computer> <Security UserID="S-1-5-18" /> </System>
<EventData> <Data Name="AppName">MsMpEng.exe</Data> <Data Name="AppVersion">4.18.26070.9</Data> <Data Name="AppTimeStamp">9a78fc05</Data> <Data Name="ModuleName">mpengine.dll</Data> <Data Name="ModuleVersion">1.1.26070.7</Data> <Data Name="ModuleTimeStamp">a09e75a9</Data> <Data Name="ExceptionCode">c0000005</Data> <Data Name="FaultingOffset">000000000092e48b</Data> <Data Name="ProcessId">0x10e0</Data> <Data Name="ProcessCreationTime">0x1dd2f5a07d619cb</Data> <Data Name="AppPath">C:\ProgramData\Microsoft\Windows Defender\Platform\4.18.26070.9-0\MsMpEng.exe</Data> <Data Name="ModulePath">C:\ProgramData\Microsoft\Windows Defender\Definition Updates{F51C2D1B-440B-4462-93CE-D318FB618CBE}\mpengine.dll</Data> <Data Name="IntegratorReportId">e59a6c0e-ab67-4671-8495-e91cab718fc1</Data> <Data Name="PackageFullName" /> <Data Name="PackageRelativeAppId" /> </EventData> </Event>

Robert Bonin 5 Reputation points

2026-08-18T22:12:34.2366667+00:00

A number of us are experiencing the same issue following the 8/18/26 update to Microsoft Security software. Following the update, we can no longer perform a virus and threat detection scan. The attempted scan does not successfully complete its run, and the following message is displayed: "Threat service has stopped. Restart it now." Following the attempted service restart, scans will still not work. So, we have no ability to detect and repair security threats. I contacted the Windows Security Response Center to report this and was told that this issue does not meet the definition of a security vulnerability! So, no action or solution is being provided by Microsoft for problems introduced by the latest software release to their security software. This is unacceptable.
Xander Warren 50 Reputation points

2026-08-18T22:16:17.9533333+00:00

did they at least mention looking into a fix?
Robert Bonin 5 Reputation points

2026-08-18T22:30:23.0566667+00:00

No. They pretty much blew it off. No help whatsoever was provided from their Security Response Center. I am not sure where to go from here. Microsoft is providing no help at all for risks introduced by their software release.
Taiwendo 0 Reputation points

2026-08-18T22:34:22.61+00:00

I have exactly the same problem.

I’ve already wasted three hours of my life today trying to fix these errors.

But unfortunately, to no avail. Just before I was about to reinstall my system, I checked Reddit and saw that a lot of people were having the same problem and realized, “Oh, MS has messed up again.”

I’ve had this problem since the five updates that rolled out over the past 14 hours today.

None of the updates have fixed the problem for Defender so far.

The file “mpengine.dll” seems to have a problem with a digital signature.
Xander Warren 50 Reputation points

2026-08-18T22:51:55.1233333+00:00

something about access violation as well this is what my chain of crash looks like for me. It seems to always be the same too.
MsMpEng.exe → mpengine.dll → 0xc0000005 → 0x92e48b

All we can do is wait for them to push out an update that'll fix it.
Xander Warren 50 Reputation points

2026-08-18T23:42:45.3+00:00

I checked when my last scan was, it was 1:16AM on august 18th so sometime after that the pushed a defender update that broke it for me and others.
Xander Warren 50 Reputation points

2026-08-19T01:32:25.2266667+00:00

I downloaded Malwarebytes so I have a way to scan my pc and have an active anti-virus tool that I can use. Just for peace of mind

2 answers

Your answer

Robert Bonin 5 Reputation points

2026-08-18T22:12:34.2366667+00:00

A number of us are experiencing the same issue following the 8/18/26 update to Microsoft Security software. Following the update, we can no longer perform a virus and threat detection scan. The attempted scan does not successfully complete its run, and the following message is displayed: "Threat service has stopped. Restart it now." Following the attempted service restart, scans will still not work. So, we have no ability to detect and repair security threats. I contacted the Windows Security Response Center to report this and was told that this issue does not meet the definition of a security vulnerability! So, no action or solution is being provided by Microsoft for problems introduced by the latest software release to their security software. This is unacceptable.
Xander Warren 50 Reputation points

2026-08-18T22:16:17.9533333+00:00

did they at least mention looking into a fix?
Robert Bonin 5 Reputation points

2026-08-18T22:30:23.0566667+00:00

No. They pretty much blew it off. No help whatsoever was provided from their Security Response Center. I am not sure where to go from here. Microsoft is providing no help at all for risks introduced by their software release.
Taiwendo 0 Reputation points

2026-08-18T22:34:22.61+00:00

I have exactly the same problem.

I’ve already wasted three hours of my life today trying to fix these errors.

But unfortunately, to no avail. Just before I was about to reinstall my system, I checked Reddit and saw that a lot of people were having the same problem and realized, “Oh, MS has messed up again.”

I’ve had this problem since the five updates that rolled out over the past 14 hours today.

None of the updates have fixed the problem for Defender so far.

The file “mpengine.dll” seems to have a problem with a digital signature.
Xander Warren 50 Reputation points

2026-08-18T22:51:55.1233333+00:00

something about access violation as well this is what my chain of crash looks like for me. It seems to always be the same too.
MsMpEng.exe → mpengine.dll → 0xc0000005 → 0x92e48b

All we can do is wait for them to push out an update that'll fix it.
Xander Warren 50 Reputation points

2026-08-18T23:42:45.3+00:00

I checked when my last scan was, it was 1:16AM on august 18th so sometime after that the pushed a defender update that broke it for me and others.
Xander Warren 50 Reputation points

2026-08-19T01:32:25.2266667+00:00

I downloaded Malwarebytes so I have a way to scan my pc and have an active anti-virus tool that I can use. Just for peace of mind

Answer 1

Ramesh 180.1K Volunteer Moderator

Microsoft fixes known issue causing Windows Defender crashes:
https://www.bleepingcomputer.com/news/microsoft/microsoft-fixes-known-issue-causing-windows-defender-crashes/

Xander Warren 50 Reputation points

2026-08-19T18:41:36.1633333+00:00

seems to be fixed for me, it's unacceptable that this security update was pushed out without proper testing though. It happened to all of my friends and countless others.

Answer 2

Thoura Sopheak Nanta 655

Hi @Robert Bonin @Taiwendo @Xander Warren

This is a real, widespread Microsoft Defender problem that occurred on August 18, 2026.

Your PC is not infected; it's just Defender crashing on its own.

Try updating your computer through Windows Update.

If it still fails, open PowerShell as admin and run:

Update-MpSignature

This should force Defender to update.

Best regards,

Nanta

Xander Warren 50 Reputation points

2026-08-19T04:42:54.5033333+00:00

I've already done that, defender is fully up to date