CVE-2020-1054
📋 TL;DR
This vulnerability allows local attackers to escalate privileges on Windows systems by exploiting a memory handling flaw in the Win32k kernel driver. Attackers can gain SYSTEM-level privileges from a lower-privileged account. Affects Windows operating systems with vulnerable kernel versions.
💻 Affected Systems
- Microsoft Windows
📦 What is this software?
Windows 10 1507 by Microsoft
Windows 10 1507 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1709 by Microsoft
Windows 10 1709 by Microsoft
Windows 10 1709 by Microsoft
Windows 10 1803 by Microsoft
Windows 10 1803 by Microsoft
Windows 10 1803 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 1903 by Microsoft
Windows 10 1903 by Microsoft
Windows 10 1903 by Microsoft
Windows 10 1909 by Microsoft
Windows 10 1909 by Microsoft
Windows 10 1909 by Microsoft
Windows 7 by Microsoft
Windows 8.1 by Microsoft
Windows Rt 8.1 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with SYSTEM privileges, enabling installation of malware, data theft, persistence mechanisms, and lateral movement across the network.
Likely Case
Local privilege escalation allowing attackers to bypass security controls, install backdoors, or access restricted system resources.
If Mitigated
Limited impact if proper patch management and least privilege principles are enforced, though local users could still attempt exploitation.
🎯 Exploit Status
Proof-of-concept code is publicly available and has been weaponized in real attacks. Requires local user execution.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: May 2020 security updates (KB4556799 for Windows 10 1903/1909)
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1054
Restart Required: Yes
Instructions:
1. Apply Windows Update KB4556799 via Windows Update or WSUS. 2. For manual installation, download from Microsoft Update Catalog. 3. Restart system after installation.
🔧 Temporary Workarounds
Restrict local user privileges
windowsImplement least privilege principle to limit impact of successful exploitation
Enable Windows Defender Exploit Guard
windowsUse exploit protection to mitigate kernel exploitation attempts
Set-ProcessMitigation -System -Enable CFG, ForceRelocateImages, BottomUpASLR, HighEntropyASLR
🧯 If You Can't Patch
- Implement strict access controls and limit local administrative privileges
- Monitor for suspicious process creation and privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check Windows build number: winver command should show build 18362.836 or 18363.836 for Windows 10 1903/1909 respectively. Lower builds are vulnerable.Check Version:
winver or systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify KB4556799 is installed via: wmic qfe list | findstr KB4556799📡 Detection & Monitoring
Log Indicators:
- Event ID 4688 with privileged process creation from non-privileged users
- Unexpected SYSTEM privilege acquisition
- Win32k.sys related crashes or errors
Network Indicators:
- Not applicable - local exploitation only
SIEM Query:
EventID=4688 AND NewProcessName="*" AND SubjectUserName!="SYSTEM" AND TokenElevationType="%%1938"🔗 References
- http://packetstormsecurity.com/files/160515/Microsoft-Windows-DrawIconEx-Local-Privilege-Escalation.html
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1054
- http://packetstormsecurity.com/files/160515/Microsoft-Windows-DrawIconEx-Local-Privilege-Escalation.html
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1054
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-1054
