Microsoft Patches ‘RoguePlanet’ Zero-Day in Defender After June Patch Tuesday

Microsoft has released a security patch to address a zero-day vulnerability in its Microsoft Defender antivirus software, tracked as “RoguePlanet.” The flaw was disclosed after the June 2026 Patch Tuesday, prompting an out-of-band update.

The RoguePlanet exploit allows attackers to gain extensive system rights on Windows machines. According to the advisory, the vulnerability could be leveraged to elevate privileges, potentially giving threat actors full control over affected systems.

Microsoft responded with an emergency update for Defender, urging users to apply the patch promptly to protect against active exploitation. The company did not disclose whether the flaw had been used in targeted attacks prior to the fix.

The update is available through Windows Update and the Microsoft Update Catalog. Security experts recommend immediate installation, as the exploit code could enable further compromise if left unpatched.