Microsoft Defender bug causing crashes resolved

Microsoft has resolved a bug that caused Windows Defender to crash, leading to 0xc0000005 access violation errors on some systems. The issue, which began Tuesday afternoon, prompted users to restart the Defender service or, in some cases, reinstall the operating system. Microsoft has since confirmed the bug has been addressed in a new signature update, based on information published by Bleeping Computer.

The bug caused Windows Defender quick or full scans to fail, sometimes requiring the service to be restarted. System administrators reported encountering the issue, initially suspecting it was related to existing infections, but later found it could be recreated on other devices simply by initiating a quick scan. Microsoft has released a fix via Microsoft Defender Antivirus signature update version 1.457.236.0 or later. Users are advised to ensure their systems are updated and that they have the latest security intelligence update installed.

This incident follows previous issues with Microsoft Defender, including a false-positive alert in May that flagged DigiCert root certificates as malware and a portal outage in December 2025 that disrupted security alerts.

Source: Bleeping Computer