New Windows Zero-Day Exploit ‘RoguePlanet’ Released

A security researcher has released another zero-day exploit targeting Microsoft’s Windows operating system, shortly after Redmond rolled out its Patch Tuesday updates. Dubbed RoguePlanet, the proof-of-concept (PoC) exploit was released by Nightmare Eclipse (also known as Chaotic Eclipse), who dropped several zero-days in Microsoft products over the past couple of months. The fresh zero-day exploit leads to local privilege escalation (LPE) by exploiting a race condition issue in Microsoft Defender, Nightmare Eclipse says. According to the researcher, the exploit initially led to remote code execution (RCE) by tricking a victim into opening a .vhd(x) file on a remote SMB server or into opening the SMB share.  The exploit could also lead to BitLocker bypass using a specialized device designed to push data to NTFS.sys. Once Defender reads the malicious file, the exploit would redirect the cleaned file to a new location.  Mitigations rolled out by Microsoft in May, however, closed some of the attack paths, and the researcher had to rework the exploit, which took a lot of effort. At the moment, it is unclear whether RoguePlanet is limited to LPE or could be redesigned to achieve RCE as well. The PoC may not work reliably at all times, but has been tested on Windows 11 and Windows 10 machines with the June 2026 patches installed, the researcher notes, adding that it does not work on Windows Server. “I’m confident that all Windows Server versions are vulnerable as well, but by the time I figured out that the PoC doesn’t work in Windows Server installations, it was too late to redesign the exploit to overcome this issue,” the researcher says. Nightmare Eclipse also says that, with more effort, the PoC could be refined to work on all systems.  Shortly after RoguePlanet was published, several security researchers validated that it can be used on patched computers to spawn a command prompt window with SYSTEM privileges. The new zero-day was dropped just as Microsoft shipped patches for two exploits released by Nightmare Eclipse, namely GreenPlasma and YellowKey. These appear to correspond to CVE-2026-45586 and CVE-2026-50507, an elevation of privilege in CTFMON and a BitLocker bypass fixed with the June 2026 Patch Tuesday updates. Previously, Microsoft rolled out patches for other exploits disclosed by Nightmare Eclipse, including RedSun (CVE-2026-41091), UnDefend (CVE-2026-45498), and BlueHammer (CVE-2026-33825), which have been exploited in the wild. Nightmare Eclipse has dropped the exploits after expressing discontent with Microsoft’s vulnerability disclosure process and with how the company treated the researcher in the past. In response, Microsoft called for responsible disclosure, saying it would pursue legal action against anyone engaging in malicious cyber activities or helping miscreants. After its remarks sparked backlash from the cybersecurity community, the tech giant clarified that it would not “pursue action against individuals conducting or publishing their security research.” However, Nightmare Eclipse has suggested that the company did file legal action against them. Microsoft also suspended the researcher’s account on GitHub, and the RoguePlanet exploit was published on a fresh account, named MSNightmare. Related: Researcher Drops MiniPlasma Windows Exploit for Unpatched 2020 CVE Related: No Patch Planned for Exploited Arista EOS Vulnerability Related: Critical Vulnerabilities Patched in Fortinet, Ivanti Products Related: Gogs Zero-Day Exposes Servers to Remote Code Execution WRITTEN BY Ionut Arghire Ionut Arghire is an international correspondent for SecurityWeek. 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