ShieldBreak: New Windows Zero-Day Bypasses Microsoft’s RoguePlanet Patch
Researcher Chaotic Eclipse published a PoC bypassing Microsoft's CVE-2026-50656 Defender patch, enabling SYSTEM-level code execution on fully patched Windows systems.
Security researcher Chaotic Eclipse released a proof-of-concept for ShieldBreak, a Microsoft Defender zero-day that fully bypasses the patch for CVE-2026-50656 (RoguePlanet), a race condition in the Malware Protection Engine (mpengine.dll) allowing SYSTEM-level code execution. The PoC was tested on Windows 11 25H2 and Windows Server 2025 with a 100% success rate, and Windows 10 is also vulnerable though not supported by the PoC; the flaw may also leak 8 bytes of memory. Microsoft's MSRC had criticized the researcher's repeated uncoordinated disclosures, including YellowKey (BitLocker bypass), GreenPlasma, and LegacyHive (User Profile Service LPE).
China-Linked Hackers Exploit Chrome and Windows Zero-Days in BlueMoon Attacks
China-linked clusters deploy the BlueMoon kit chaining Chrome V8 CVE-2026-85046 and Windows LPE CVE-2026-85880 in espionage campaigns.
Proofpoint researchers identified BlueMoon, an exploit kit combining a V8 type-confusion RCE (CVE-2026-85046), a V8 sandbox escape, and a Windows kernel privilege-escalation flaw (CVE-2026-85880), first observed August 28, 2026. At least four clusters adopted it, led by TA412 (also tracked as APT31/Violet Typhoon) and followed by UNK_LateNight, UNK_DoubleCheck, and UNK_QuietRacket, targeting aerospace, manufacturing, government, consulting, and financial sectors. The kit exploited a nearly four-week patch gap between the public Chromium commit (August 7) and stable rollout (September 3). TA412 delivered the GemStone Chrome extension masquerading as a Gemini companion, while other clusters deployed ShadowPad via DLL sideloading, a Rust loader, and DoH-based C2.
Microsoft Patches Record 974 Flaws, Including Two Exploited Windows Zero-Days
Microsoft's September Patch Tuesday fixed a record 974 flaws, including two Windows privilege-escalation zero-days actively exploited and added to CISA's KEV catalog.
Microsoft's September 2026 Patch Tuesday addressed a record 974 vulnerabilities (999 including 25 non-Microsoft CVEs), with over 110 rated critical; 723 affect Windows and 111 affect Office. Two Windows privilege-escalation zero-days are actively exploited: CVE-2026-85880, an ALPC heap-based buffer overflow, and CVE-2026-81963, an improper link resolution flaw in the Windows Update Stack, both allowing attackers to gain SYSTEM privileges. CISA added both flaws to its KEV catalog, giving federal civilian agencies until September 22, 2026 to apply fixes. Volexity, Proofpoint, MSTIC, and independent researchers were credited with the reports; notable additional fixes include network-reachable RCEs in Exchange, SharePoint, SQL Server, Remote Desktop Services, DNS, and DHCP.
2026-007: Critical Vulnerability in Windows Netlogon
Actively exploited CVSS 9.8 Windows Netlogon flaw lets unauthenticated attackers execute code with SYSTEM privileges on domain controllers.
Microsoft's May 2026 advisory describes CVE-2026-41089, a stack-based buffer overflow in Windows Netlogon (CVSS 9.8) that allows unauthenticated remote code execution with SYSTEM privileges on domain controllers via specially crafted packets. The Centre for Cybersecurity Belgium reports the flaw is currently being exploited by threat actors. All Windows Server versions from 2012 through 2025 acting as domain controllers are affected and require the May updates.