Microsoft working on Defender patch for ShieldBreak zero-day

Microsoft is actively working on a patch for a new zero-day vulnerability named ShieldBreak in Microsoft Defender, which allows privilege escalation by bypassing a previously patched flaw called RoguePlanet. The vulnerability was disclosed publicly without prior notice by the researcher Nightmare Eclipse, escalating tensions over vulnerability disclosure practices.

This Wire brief sits within Fusion42's coverage of Cybersecurity, and 3 sources have reported it between 12 Aug 2026 and 17 Aug 2026.