Microsoft Issues Emergency Patch for RoguePlanet Windows Defender Zero-Day

Microsoft released an emergency update addressing a high-severity Windows Defender zero-day called RoguePlanet (CVE-2026-50656) that enables local privilege escalation to SYSTEM; a public proof-of-concept was published by a researcher known as Nightmare-Eclipse and the fix was delivered via Microsoft Malware Protection Engine update 1.1.26060.3008. Microsoft rated the issue CVSS 7.8, warned that systems with Defender disabled are not vulnerable, and stated there is no confirmed in-the-wild exploitation, while researchers note the public PoC increases the risk and recommend immediate patching and monitoring.