Microsoft Defender crashes after Full scan — mpengine.dll 0xc0000005

Hi,

I made an account just because I am a little curious and a little worried.

I updated to the newest Defender platform version earlier today, and it all seemed fine. However, I opened League of Legends tonight and my Microsoft Defender crashed with an exception code of 0xc0000005. When I saw this, I got scared and shut down Vanguard.

Following this, I performed a full scan while checking my Event Viewer and noticed this:
File Name: \Device\HarddiskVolume7\Windows\System32\fcon.dll

The full scan came back clean, but after 5 seconds it crashed again with the same error and fcon.dll in audit failure again.

I am wondering if this is related to the newest platform version because I was able to open League fine just the other night and there were no crashes, but after this update it has crashed upon opening League and after a full scan.

I do not believe it is malware and have no plausible evidence to believe it is such.

Thank you for any help you can provide.

Open an elevated Command prompt (Run as Administrator)

Copy/paste and run the following...

sfc /SCANNOW

Run until there are no errors found and corrected.

Banjoman301 said:

Open an elevated Command prompt (Run as Administrator)

Copy/paste and run the following...

sfc /SCANNOW

Run until there are no errors found and corrected.

Click to expand...

Thank you for the quick response, I have just ran it and it came back clean, no errors were found.

I'm not sure if this will be of any help but, It has been an hour since the last crash and this is the health report I have received:
Endpoint Protection client health report (time in UTC):
Platform version: 4.18.26100.4
Engine version: 1.1.26100.4
Network Realtime Inspection engine version: 1.1.26100.4
Antivirus security intelligence version: 1.463.16.0
Antispyware security intelligence version: 1.463.16.0
Network Realtime Inspection security intelligence version: 1.463.16.0
RTP state: Enabled
OA state: Enabled
IOAV state: Enabled
BM state: Enabled
Antivirus security intelligence age: 0
Antispyware security intelligence age: 0
Last quick scan age: 0
Last full scan age: 0
Antivirus security intelligence creation time: 2026-10-28T20:03:00Z
Antispyware security intelligence creation time: 2026-10-28T20:03:00Z
Last quick scan start time: 2026-10-28T21:49:59Z
Last quick scan end time: 2026-10-28T21:50:49Z
Last quick scan source: 1
Last full scan start time: 2026-10-28T21:51:05Z
Last full scan end time: 2026-10-28T22:24:12Z
Last full scan source: 1
Product status: 0x00080000

All the version numbers are current.

What happens if you check for an update?

It says security intelligence is up to date.

Banjoman301 said:

All the version numbers are current.

What happens if you check for an update?

Click to expand...

It says "Security intelligence is up to date."