CVE-2021-42285
📋 TL;DR
CVE-2021-42285 is a Windows kernel elevation of privilege vulnerability that allows authenticated attackers to gain SYSTEM-level privileges on affected systems. This affects Windows operating systems where an attacker with local access can exploit improper handling of objects in memory. The vulnerability requires an attacker to have initial access to execute code on the target system.
💻 Affected Systems
- Microsoft Windows
📦 What is this software?
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 11 by Microsoft
Windows 11 by Microsoft
Windows 7 by Microsoft
Windows 7 by Microsoft
Windows 8.1 by Microsoft
Windows 8.1 by Microsoft
Windows Rt 8.1 by Microsoft
Windows Server by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
An attacker gains full SYSTEM privileges, enabling complete system compromise, installation of persistent malware, credential theft, and lateral movement across the network.
Likely Case
Privilege escalation from a standard user or service account to SYSTEM, allowing attackers to bypass security controls, install additional payloads, and access sensitive system resources.
If Mitigated
With proper access controls, network segmentation, and endpoint protection, exploitation would be limited to isolated systems with minimal lateral movement capability.
🎯 Exploit Status
Exploitation requires local authenticated access. Public proof-of-concept code exists, making exploitation more accessible to attackers with moderate skill level.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: November 2021 security updates (KB5007186 for Windows 10 20H2, KB5007189 for Windows 10 21H1, etc.)
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42285
Restart Required: Yes
Instructions:
1. Apply the November 2021 Windows security updates through Windows Update. 2. For enterprise environments, deploy updates through WSUS, SCCM, or equivalent patch management system. 3. Restart systems after patch installation.
🔧 Temporary Workarounds
Restrict local administrator privileges
windowsLimit the number of users with local administrator rights to reduce attack surface
Enable Windows Defender Exploit Guard
windowsConfigure Exploit Guard to detect and block privilege escalation attempts
🧯 If You Can't Patch
- Implement strict network segmentation to contain potential lateral movement
- Deploy endpoint detection and response (EDR) solutions to detect privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check Windows version and installed updates. Systems without November 2021 security updates are vulnerable.Check Version:
wmic os get caption, version, buildnumber, csdversionVerify Fix Applied:
Verify that November 2021 security updates (KB5007186, KB5007189, or equivalent for your version) are installed.📡 Detection & Monitoring
Log Indicators:
- Windows Security Event ID 4688 (process creation) showing unexpected SYSTEM privilege processes
- Event ID 4672 (special privileges assigned to new logon) from non-admin accounts
Network Indicators:
- Unusual outbound connections from systems after local authentication events
- Lateral movement attempts from previously compromised systems
SIEM Query:
EventID=4688 AND NewProcessName="*" AND SubjectUserName!="SYSTEM" AND TokenElevationType="%%1938"