CVE-2026-50656 (‘RoguePlanet’) is an unpatched race condition in the Microsoft Malware Protection Engine — the scanning engine underlying Microsoft Defender for Endpoint, Defender Antivirus, and related Windows security components — that allows any local attacker to escalate privileges to SYSTEM on fully patched Windows 10 and Windows 11. A public proof-of-concept is available, and no patch exists from Microsoft at time of publication. Organizations must rely entirely on compensating controls and behavioral detection until Microsoft releases a fix via Windows Update.