BlueHammer Archives

Winsage

September 23, 2026

New Windows Defender zero-day blocks Microsoft antivirus updates

Security researcher Abdelhamid Naceri, known as Nightmare Eclipse, released a zero-day exploit called BigDiskBuster that targets Microsoft Defender, preventing antivirus updates and leaving systems vulnerable. BigDiskBuster operates across all supported Windows versions and must run in the background to block updates. Naceri has previously released a similar exploit called UnDefend and has a history of releasing multiple zero-day exploits since April 2026 amid a dispute with Microsoft. Two weeks before BigDiskBuster, he introduced another exploit named ShieldCrash, which grants SYSTEM access and circumvents a patched flaw. Naceri's recent exploits include tools like LegacyHive, BlueHammer, RedSun, YellowKey, GreenPlasma, and MiniPlasma, all targeting Microsoft Defender and other Windows components. Microsoft has warned of potential legal action against malicious activities but has not commented on BigDiskBuster.

Winsage

July 16, 2026

Nightmare Eclipse Drops ‘LegacyHive’ Windows Zero-Day

A security researcher known as Nightmare Eclipse has revealed a new unpatched vulnerability in Windows, named LegacyHive, which is a local privilege escalation flaw in the Windows User Profile Service. This vulnerability allows attackers to access and load user hives of other accounts, including administrators. Nightmare Eclipse has provided proof-of-concept exploit code that works on systems with Microsoft's July 2026 patches. The exploit initially did not require user credentials but now necessitates them for accessing other hives. Nightmare Eclipse has previously disclosed over half a dozen zero-day vulnerabilities affecting Microsoft products. Microsoft has not yet acknowledged the LegacyHive exploit.

Winsage

June 30, 2026

Windows Defender ‘BlueHammer’ vulnerability now exploited as part of malware campaigns — CISA issues warning despite patch release on April 14

A race condition vulnerability in Windows Defender, known as BlueHammer, has been exploited by the hacker Nightmare Eclipse, allowing attackers to gain SYSTEM user access. Microsoft released a patch for this vulnerability on April 14, but the Cybersecurity and Infrastructure Security Agency (CISA) has flagged it as actively exploited in ransomware campaigns. The average time to apply critical OS patches across Windows 10 and 11 is now 127 days, with enterprise environments averaging 76 days. Estimates suggest that 15% to 26% of Windows 10 machines remain unpatched, with a conservative estimate of 20% translating to one in five machines being vulnerable. Microsoft has extended security updates for Windows 10 until October 14, 2027, but public awareness of the updates remains low.