A security researcher known as Nightmare Eclipse has released a new Microsoft Defender zero-day exploit named "ShieldBreak" after Microsoft released the August 2026 Patch Tuesday security updates.
The new vulnerability is described as a bypass for RoguePlanet, another Defender privilege escalation flaw disclosed in June and patched by Microsoft one month later.
As Nightmare Eclipse explained, ShieldBreak can be used to gain SYSTEM privileges on fully patched Windows 10, Windows 11, and Windows Server systems.
"Microsoft has failed to properly patch the RoguePlanet vulnerability CVE-2026-50656, this PoC demonstrates a full patch bypass," they said.
"The PoC was tested in the latest version of windows 11 25h2 (+Canary channel) and windows server 2025, the PoC also have a 100% success rate. Please note that Windows 10 (and respective server editions) are not currently supported, they are however vulnerable to ShieldBreak as well."
