CVE-2021-21787
📋 TL;DR
This vulnerability allows local attackers to escalate privileges by writing arbitrary bytes to I/O device ports through a vulnerable driver in IOBit Advanced SystemCare Ultimate. It affects users running the vulnerable software version on Windows systems. Successful exploitation could give unprivileged users SYSTEM-level access.
💻 Affected Systems
- IOBit Advanced SystemCare Ultimate
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with SYSTEM privileges, allowing installation of malware, data theft, or persistence mechanisms.
Likely Case
Local privilege escalation enabling attackers to bypass security controls, install additional malware, or access protected resources.
If Mitigated
Limited impact if proper endpoint protection and least privilege principles are enforced, though local escalation remains possible.
🎯 Exploit Status
Exploitation requires local access and knowledge of the IOCTL interface. The vulnerability is well-documented with technical details available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 14.2.0.221 or later
Vendor Advisory: https://www.iobit.com/en/advancedsystemcarepro.php
Restart Required: Yes
Instructions:
1. Open Advanced SystemCare Ultimate. 2. Click 'Check for Updates'. 3. Install available updates. 4. Restart the system to ensure the vulnerable driver is replaced.
🔧 Temporary Workarounds
Disable or Remove Advanced SystemCare
windowsUninstall the vulnerable software to eliminate the attack vector
Control Panel > Programs > Uninstall a program > Select Advanced SystemCare Ultimate > Uninstall
Restrict Driver Access
windowsUse application control policies to block execution of the vulnerable driver
🧯 If You Can't Patch
- Implement strict least privilege principles to limit user access
- Deploy endpoint detection and response (EDR) solutions to monitor for privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check the installed version of Advanced SystemCare Ultimate in Control Panel > Programs > Programs and FeaturesCheck Version:
wmic product where name="Advanced SystemCare Ultimate" get versionVerify Fix Applied:
Verify the version is 14.2.0.221 or later after updating📡 Detection & Monitoring
Log Indicators:
- Driver load events for the vulnerable driver
- Process creation with elevated privileges from non-admin users
Network Indicators:
- Local privilege escalation typically doesn't generate network traffic
SIEM Query:
EventID=4688 AND NewProcessName="*" AND SubjectUserName!="SYSTEM" AND TokenElevationType="%%1938"