CVE-2026-50656 (RoguePlanet) is an unpatched race condition in the Microsoft Malware Protection Engine (MsMpEng) within Microsoft Defender that allows local privilege escalation to SYSTEM on all fully patched Windows 10 and Windows 11 endpoints, with a public proof-of-concept already in circulation. No patch or workaround has been issued by Microsoft. Two sibling vulnerabilities in the same Nightmare Eclipse series are reported as actively exploited, making imminent in-the-wild exploitation of CVE-2026-50656 a high-probability near-term scenario.