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ShieldBreak PoC claims full Microsoft Defender patch bypass with SYSTEM access

Feeds.4Sysops •IT News • August 12, 2026

A new ShieldBreak proof of concept claims to bypass Microsoft’s fix for the RoguePlanet vulnerability in Microsoft Defender, restoring a path to SYSTEM-level privileges. Testing reportedly succeeded on fully updated Windows 11 25H2 and Windows Server 2025 systems, while Windows 10 is also considered vulnerable. Source

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This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

New Windows Zero-Day 'ShieldBreak' Exploits Microsoft Defender Flaw Security researcher Nightmare Eclipse has disclosed a new zero-day vulnerability named ShieldBreak, which allows attackers to gain SYSTEM-level privileges on fully patched Windows 10, Windows 11, and Windows Server systems. The exploit bypasses Microsoft's previous patch for the RoguePlanet vulnerability (CVE-2026-50656), which was intended to address a local privilege escalation flaw. Nightmare Eclipse claims that the proof of concept (PoC) for ShieldBreak has a 100% success rate when tested on the latest Windows 11 version and Windows Server 2025. The exploit leverages interactions between Microsoft Defender and filesystem objects, tricking Defender into executing malicious code. This release follows a pattern of disclosures by Nightmare Eclipse, who has previously published multiple zero-day exploits against Microsoft products. Microsoft has not yet issued a patch for ShieldBreak, leaving users vulnerable until a fix is released. Experts have confirmed the exploit's functionality, raising concerns about its potential for widespread abuse. 59 sources 70

Extracted Entities

ShieldBreak PoC claims full Microsoft Defender patch bypass with SYSTEM access

The full story

Extracted Entities

Attack Types (1)

CWE Weaknesses (1)

MITRE ATT&CK (1)

Platforms (3)

Vulnerabilities (1)