ShieldBreak Exploit Bypasses Microsoft Defender Patch for Privilege Escalation

A security researcher has released a proof-of-concept exploit for a new zero-day vulnerability in Microsoft Defender, claiming it fully bypasses the company's recent patch for a previously disclosed flaw. The exploit, named ShieldBreak, targets Windows 11 25H2 and Windows Server 2025 and could allow an attacker with initial access to a system to escalate privileges to the highest level.

The researcher, who uses the online aliases NightmareEclipse and Chaotic Eclipse, announced the release on August 12, 2026. ShieldBreak is described as a bypass for CVE-2026-50656, a vulnerability known as RoguePlanet that Microsoft patched in its July 2026 security updates. The researcher stated that the new exploit demonstrates a "full patch bypass" and has a "100% success rate" in tests on the latest versions of Windows 11 and Windows Server 2025. While the proof-of-concept code does not currently support Windows 10, the researcher noted that the operating system is also vulnerable.

The exploit is a local privilege escalation flaw, meaning it does not allow remote hacking but enables an attacker who already has code execution on a target machine to gain SYSTEM privileges. This level of access...