Researcher Discloses Windows Zero-Day Exploit PoC Post-Patch Tuesday Update

A researcher disclosed a proof-of-concept exploit for a Windows User Profile Service vulnerability affecting all supported Windows versions, including systems patched during the July 2026 Patch Tuesday. The exploit enables privilege escalation through arbitrary hive loading, raising concerns about Microsoft's vulnerability disclosure processes.

Security researcher Chaotic Eclipse (aka Nightmare-Eclipse) has released a new proof-of-concept (PoC) exploit called LegacyHive.

It has been described as a Windows User Profile Service arbitrary hive load elevation of privileges vulnerability. The Windows User Profile Service, also referred to as ProfSvc, is a core system component that manages user accounts and environments.

"The PoC requires

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