CVE-2026-41091-PoC-Exploit Full-PoCv2
Local privilege escalation exploit for CVE-2026-41091 targeting Microsoft Defender. Uses Cloud Files API and NTFS junction redirection to gain NT AUTHORITY\SYSTEM from a low-privileged user. Includes full PoC and educational algorithm demonstration.
☀️ CVE-2026-41091 - RedSun (SolarFlare) - Microsoft Defender LPE Exploit
Microsoft Defender Link Following Vulnerability - Local Privilege Escalation to NT AUTHORITY\SYSTEM
The vulnerability is known as "RedSun" 🎯, "SolarFlare" is the name I gave to my exploit. ✅
📌 Overview
This repository contains a full working Proof of Concept (PoC) exploit for CVE-2026-41091, a critical local privilege escalation vulnerability in Microsoft Defender (Microsoft Malware Protection Engine). By exploiting improper link resolution (CWE-59), an authenticated low-privileged attacker can gain NT AUTHORITY\SYSTEM privileges.
The vulnerability, also known as "RedSun" or "SolarFlare", allows attackers to trick Microsoft Defender into writing arbitrary files to protected system locations with SYSTEM privileges using Cloud Files API (CfAPI) and NTFS junction points.
Note: This repository includes two versions:
basic_poc.cpp- Simplified algorithm demonstration (educational)full_poc.cpp- Complete working exploit with all features
🔥 Key Features
| Category | Features |
|---|---|
| Exploitation | ✅ Local Privilege Escalation to SYSTEM ✅ Cloud Files API (CfAPI) Integration ✅ Cloud Placeholder Creation ✅ NTFS Junction Redirection |
| Techniques | ✅ Batch Oplock Abuse ✅ VSS Snapshot Detection ✅ EICAR Trigger ✅ COM Service Activation |
| Target | ✅ Microsoft Defender < 1.1.26040.8 ✅ Windows 10/11 ✅ Windows Server 2019/2022 |
| Usability | ✅ Detailed Logging ✅ Error Handling ✅ Random Directory Names ✅ Automatic Cleanup |
🎯 Vulnerability Details
| Attribute | Value |
|---|---|
| CVE ID | CVE-2026-41091 |
| CVSS Score | 7.8 (High) |
| CVSS Vector | AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| Attack Vector | Local |
| Privileges Required | Low |
| User Interaction | None |
| Impact | SYSTEM-level code execution |
| CISA KEV | ✅ Yes (actively exploited in the wild) |
| Patch Available | Microsoft Malware Protection Engine 1.1.26040.8 |
📦 Affected Products
| Product | Affected Versions | Fixed Versions |
|---|---|---|
| Microsoft Malware Protection Engine | < 1.1.26040.8 | 1.1.26040.8+ |
| Microsoft Defender Antimalware Platform | < 4.18.26040.7 | 4.18.26040.7+ |
🔬 Exploit Chain
┌─────────────────────────────────────────────────────────────────────────────┐
│ SOLARFLARE EXPLOIT CHAIN │
├─────────────────────────────────────────────────────────────────────────────┤
│ │
│ 1. Create Working Directory │
│ └─> %TEMP%\SF-XXXX\ │
│ │
│ 2. Trigger Defender with EICAR │
│ └─> Write reversed EICAR to bait file │
│ │
│ 3. Wait for VSS Snapshot │
│ └─> Detect Volume Shadow Copy creation │
│ │
│ 4. Create First Batch Oplock │
│ └─> FSCTL_REQUEST_BATCH_OPLOCK on bait file │
│ │
│ 5. Wait for Oplock Break │
│ └─> Acquire exclusive access │
│ │
│ 6. Rename Directory │
│ └─> Move original directory to .tmp │
│ │
│ 7. Register Cloud Sync Root │
│ └─> CfRegisterSyncRoot with Cloud Files API │
│ │
│ 8. Create Cloud Placeholder │
│ └─> CfCreatePlaceholders for bait file │
│ │
│ 9. Create Second Batch Oplock │
│ └─> FSCTL_REQUEST_BATCH_OPLOCK on cloud placeholder │
│ │
│ 10. Wait for Second Oplock Break │
│ └─> Acquire exclusive access │
│ │
│ 11. Rename Cloud Directory │
│ └─> Move cloud directory to .cloud.tmp │
│ │
│ 12. Create NTFS Junction to System32 │
│ └─> Redirect to C:\Windows\System32 │
│ │
│ 13. Copy Payload to System32 │
│ └─> Copy bait file to System32 as TieringEngineService.exe │
│ │
│ 14. Activate Service as SYSTEM │
│ └─> CoCreateInstance(StorageTiersManagement) │
│ │
└─────────────────────────────────────────────────────────────────────────────┘
📦 Installation
Prerequisites
- Windows 10/11 or Windows Server 2019/2022
- Visual Studio 2019/2022 with C++ tools
- Administrative privileges (for execution)
Build
# Clone the repository
git clone https://github.com/tc4dy/CVE-2026-41091-PoC-Exploit
cd CVE-2026-41091-PoC-Exploit
# Build using Visual Studio Developer Command Prompt
cl.exe /EHsc /std:c++17 full_poc.cpp /link cfapi.lib ntdll.lib
# Or build basic version
cl.exe /EHsc /std:c++17 basic_poc.cpp /link ntdll.lib
🛠️ Usage
Full Exploit (SYSTEM Privilege Escalation)
full_poc.exe
Basic Algorithm Demonstration
basic_poc.exe
📋 Example Output
Full Exploit Output
CVE-2026-41091 SolarFlare PoC
===============================
by @tc4dy | CVSS 7.8
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