New Microsoft Defender 'ShieldCrash' zero-day grants SYSTEM access

An anonymous security researcher known as Nightmare Eclipse disclosed a new zero-day exploit named 'ShieldCrash' that exploits an incomplete patch for the previously patched Microsoft Defender privilege escalation vulnerability CVE-2026-69414 (ShieldBreak). The exploit allows attackers to achieve arbitrary file read with SYSTEM privileges on fully patched Windows 10, Windows 11, and Windows Server systems. This disclosure is part of an ongoing dispute between the researcher and Microsoft over bug bounty and vulnerability disclosure practices. Microsoft has not yet patched this newly revealed bypass.

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