Unpatched 'RedSun' Zero-Day in Microsoft Defender Poses Immediate Threat
In April 2026, security researcher Chaotic Eclipse publicly disclosed a zero-day vulnerability in Microsoft Defender, named 'RedSun.' This flaw allows local attackers to escalate privileges to SYSTEM level by exploiting a logic error in Defender's handling of specific file metadata. The vulnerability affects Windows 10, Windows 11, and Windows Server systems with Defender enabled. The researcher released a proof-of-concept (PoC) exploit on GitHub, demonstrating the ease of exploitation. Microsoft has not yet issued a patch for this vulnerability, leaving systems at risk. The public disclosure of 'RedSun' underscores the critical need for timely vulnerability management and the potential consequences of strained relationships between researchers and vendors. Organizations should monitor for updates and consider implementing additional security measures to mitigate the risk posed by this unpatched flaw.
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