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New Microsoft Defender 'ShieldBreak' zero-day grants SYSTEM privileges

August 12, 2026 · BleepingComputer · Severity: CRITICAL

Nightmare Eclipse publicly disclosed a Microsoft Defender zero-day named ShieldBreak after the August 2026 Patch Tuesday security updates. The exploit enables local attackers to escalate privileges to SYSTEM, bypassing Defender's protections. Microsoft has not yet released a patch, leaving affected systems vulnerable.

Key Takeaways

  • New Microsoft Defender zero-day 'ShieldBreak' grants attackers full SYSTEM privileges.
  • Exploit released by Nightmare Eclipse after August 2026 Patch Tuesday updates.
  • No official fix yet, leaving Defender users exposed to privilege escalation.
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