Microsoft 365 threat report

A proof-of-concept denial-of-service technique named BigDiskBuster, published on GitHub on September 21, 2026, can prevent Windows Defender from completing platform and security intelligence signature updates. The technique exploits unspecified Windows behavior to block Defender's update mechanisms, potentially leaving endpoints with outdated malware detections and reduced protection against new threats. No official CVE has been assigned, and Microsoft has not yet acknowledged the issue. The proof-of-concept code is written in C++ and has garnered significant GitHub interest (130+ stars, 20+ forks).

• BigDiskBuster Windows Defender DoS Vulnerability Blocks Platform(opens in a new tab)
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