TOCTOU

TL;DR MiniPlasma is a Windows local privilege escalation exploit that achieves standard user → SYSTEM on fully patched Windows 11 systems (including the May 2026 Patch Tuesday updates). The jaw-dropper? It targets the exact same vulnerability that Google Project Zero reported in September 2020 and Microsoft claimed to fix in December 2020. CVE: CVE-2020-17103 (CVSS 7.0) — supposedly patched Component: cldflt.sys — Windows Cloud Files Minifilter driver Flaw: TOCTOU race condition in HsmOsBlockPlaceholderAccess Impact: Full SYSTEM shell from standard user Affected: All Windows versions (confirmed on Win11 with May 2026 updates) Not affected: Latest Windows 11 Insider Preview Canary builds (suggests a fix may be incoming) Researcher: Chaotic Eclipse / Nightmare-Eclipse Public PoC: github.com/Nightmare-Eclipse/MiniPlasma The Ghost Patch Problem In cybersecurity, few things are more unsettling than a patch that never actually landed. That’s exactly what happened here. ...

Overview Attribute Value CVE ID CVE-2026-33825 CVSS Score 7.8 Vendor Microsoft Product Windows Defender Antivirus (Windows 10/11, Server 2016+) Vulnerability Type TOCTOU + Path Confusion → Local Privilege Escalation Status ✅ Patched (April 14, 2026 Patch Tuesday) CWE CWE-367 (Time-of-check Time-of-use Race Condition) KEV Added Not yet Exploitation Status ⚠️ PoC public, no confirmed in-the-wild attacks yet Patch Status ❌ Unpatched (as of April 12, 2026) Affected Versions Version Status Windows 10 (1709+) ❌ Vulnerable Windows 11 ❌ Vulnerable Windows Server 2016+ ⚠️ Partial (elevated admin, not full SYSTEM) Windows 10 (pre-1709) ✅ Not affected (no Cloud Files API) Description BlueHammer is a local privilege escalation vulnerability in Microsoft Defender Antivirus that chains a TOCTOU race condition with path confusion in Defender’s signature update workflow. A standard user can exploit Defender’s own privileged update mechanism to leak the SAM hive, decrypt credentials, and achieve SYSTEM privileges. ...

It’s been nine days since Chaotic Eclipse published the BlueHammer exploit on GitHub. Here’s what’s changed — and what hasn’t. Current Status: Still Zero-Day Attribute Status CVE Assigned ❌ No Microsoft Patch ❌ None Official Mitigation ❌ None PoC Available ✅ Original + Reimplementation Actively Exploited ⚠️ No confirmed in-the-wild attacks (yet) Detection Coverage 8/72 vendors on VirusTotal Microsoft’s last public statement (April 7) reaffirmed commitment to coordinated disclosure without addressing the MSRC communication breakdown or providing a timeline. ...

Since my initial coverage of BlueHammer, the security community has produced excellent technical analysis. This post consolidates the deep-dive details you need to understand how this exploit actually works — and why it’s more sophisticated than most LPEs. The Big Picture BlueHammer isn’t your typical privilege escalation. It doesn’t exploit a single bug — it chains seven distinct stages, weaponizing Windows Defender’s own trusted update mechanism against the system. Key insight: The exploit abuses Defender’s signature update workflow to leak the SAM hive, decrypt credentials, and achieve SYSTEM — all from a standard user context. ...