● Covered by 1 source · 2 reportsMedium impact2 neutral
Microsoft resolves Windows Defender crashing bug after recent security update
Key points
- Windows Defender crashed after a security update.
- The bug caused 0xc0000005 access violation errors.
- Microsoft released signature update 1.457.236.0 to fix the issue.
- Users are advised to update their systems.
- Microsoft asked users to ignore 'Antivirus is turned off' errors.
- The issue affects all supported Windows client and server versions, including Windows 11 26H1 and Windows Server 2025.
- The erroneous alerts appear in the Windows Security app.
- Microsoft is working on a fix for the 'Antivirus is turned off' errors.
Windows Defender Crashes Addressed
Microsoft has resolved an issue that caused Windows Defender to crash on some systems. The crashes, identified by 0xc0000005 access violation errors, occurred after a recent security update and prevented the antivirus software from performing scans and providing protection.
Impact on Users
Reports from users on social media indicated that Windows 10 and Windows 11 devices displayed "Threat service has stopped. Restart it now" messages. Some system administrators noted that quick or full scans failed, occasionally requiring the Defender service to be restarted. This disruption led some affected customers to reinstall their operating systems.
The Fix
Microsoft confirmed the bug and stated that a fix has been implemented in a new signature update. The company recommends that customers apply the latest update or enable automatic updates. The resolution is included in Microsoft Defender Antivirus signature update version 1.457.236.0 or later, which will be applied automatically.
Previous Defender Issues
This incident follows other recent issues with Microsoft Defender. In May, administrators reported that Defender incorrectly flagged DigiCert root certificates as malware, leading to false-positive alerts and certificate removal. Additionally, a widespread outage in December 2025 affected access to some Defender XDR portal capabilities and disrupted threat hunting alerts.
Updates
- Microsoft asked users to ignore 'Antivirus is turned off' errors.
- The issue affects all supported Windows client and server versions, including Windows 11 26H1 and Windows Server 2025.
- The erroneous alerts appear in the Windows Security app.
- Microsoft is working on a fix for the 'Antivirus is turned off' errors.
✨ This summary was generated by AI from the outlets' reporting listed below. It is not independently verified and may contain errors — check the original sources. How BrevFeed works →
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How outlets covered it
Microsoft has asked users to disregard erroneous notifications stating that Defender Antivirus is turned off, which appear after installing recent Defender updates. This issue affects all supported Windows client and server versions, including Windows 11 26H1 and Windows Server 2025, and Microsoft is working on a fix.
Microsoft has fixed a bug causing Windows Defender to crash with 0xc0000005 access violation errors following a recent security update. This resolution is important as the crashes prevented the security software from functioning, leaving systems vulnerable.