CVE-2020-1035
📋 TL;DR
This vulnerability allows remote code execution through the VBScript engine when it improperly handles objects in memory. Attackers can exploit this by tricking users into opening specially crafted files or visiting malicious websites. Affected systems include Windows operating systems with VBScript enabled.
💻 Affected Systems
- Microsoft Windows
- Internet Explorer
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining SYSTEM privileges, enabling data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Malware installation leading to data exfiltration, credential theft, or lateral movement within the network.
If Mitigated
Limited impact with proper patch management and application control preventing malicious script execution.
🎯 Exploit Status
Exploitation requires user interaction (opening malicious file or visiting malicious website). No public exploit code was available at disclosure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: May 2020 security updates
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1035
Restart Required: Yes
Instructions:
1. Apply May 2020 Windows security updates via Windows Update. 2. For enterprise environments, deploy updates through WSUS or SCCM. 3. Restart systems after patch installation.
🔧 Temporary Workarounds
Disable VBScript
windowsPrevents VBScript execution in Internet Explorer and other applications
reg add "HKLM\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{B54F3741-5B07-11CF-A4B0-00AA004A55E8}" /v "Compatibility Flags" /t REG_DWORD /d 0x400 /f
Restrict Internet Explorer to Internet Zone
windowsLimits VBScript execution to trusted sites only
🧯 If You Can't Patch
- Implement application control (AppLocker/Windows Defender Application Control) to block unauthorized VBScript execution
- Disable VBScript via Group Policy and restrict user permissions to prevent script execution
🔍 How to Verify
Check if Vulnerable:
Check Windows Update history for May 2020 security updates or run 'systeminfo' and verify OS build number is patchedCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify KB4556799 (Windows 10 1909/1903) or equivalent May 2020 security update is installed via 'wmic qfe list'📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing VBScript execution errors
- Process creation events for unexpected script hosts (cscript.exe, wscript.exe)
Network Indicators:
- HTTP requests to download VBScript files from untrusted sources
- SMB connections following script execution
SIEM Query:
EventID=4688 AND (NewProcessName="*cscript.exe" OR NewProcessName="*wscript.exe") AND CommandLine="*.vbs"