Security Researcher Releases PoC for Microsoft Defender Zero-Day Vulnerability ShieldBreak

A security researcher known as Chaotic Eclipse (also using aliases INFINITE NIGHTMARE, MSNightmare, and Nightmare-Eclipse) released a proof-of-concept (PoC) for a new Microsoft zero-day vulnerability named ShieldBreak. The flaw affects Microsoft Defender for Windows and demonstrates a patch bypass for CVE-2026-50656 (CVSS score: 7.8), previously identified as RoguePlanet. The PoC enables attackers to gain SYSTEM-level access on vulnerable systems. No specific disclosure date or affected software versions were provided in the report.