Security researcher Nightmare Eclipse has identified RoguePlanet, a critical zero-day vulnerability in Microsoft Defender that allows unauthorized system-level access on fully patched Windows 10 and 11 operating systems.

Key Points

• The vulnerability, tracked as CVE-2026-50656, exploits a race condition within the Microsoft Malware Protection Engine.
• Attackers can leverage this flaw to gain full system privileges on affected Windows 10 and 11 devices.
• Researcher Nightmare Eclipse released a proof-of-concept exploit after previous repositories were removed from GitHub and GitLab.
• Microsoft has officially acknowledged the threat and is currently developing a security patch for all users.
• This discovery follows a series of recent vulnerability reports by the same researcher, including flaws named BlueHammer and RedSun.

Why it Matters

This vulnerability poses a significant security risk because it grants attackers elevated control over compromised systems despite users maintaining fully updated software. Microsoft's pending patch is essential to prevent potential exploitation of this high-privilege access flaw across the Windows ecosystem.