CVE-2021-21789
📋 TL;DR
This vulnerability allows local attackers to escalate privileges by sending malicious I/O requests to the IOBit Advanced SystemCare Ultimate driver. Attackers can write arbitrary values to hardware ports, potentially gaining kernel-level access. Only users of the affected software on Windows systems are impacted.
💻 Affected Systems
- IOBit Advanced SystemCare Ultimate
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with kernel-level code execution, allowing attackers to install persistent malware, steal credentials, or disable security controls.
Likely Case
Local privilege escalation to SYSTEM/NT AUTHORITY privileges, enabling installation of additional malware or lateral movement within the network.
If Mitigated
Limited impact if proper endpoint protection and least privilege principles are enforced, though kernel access remains dangerous.
🎯 Exploit Status
Exploit requires local access but is straightforward once access is obtained. The Talos report includes technical details that could be weaponized.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 14.2.0.221 or later
Vendor Advisory: https://www.iobit.com/en/advancedsystemcareultimate.php
Restart Required: Yes
Instructions:
1. Open Advanced SystemCare Ultimate. 2. Click 'Check for Updates' or navigate to update settings. 3. Install available updates. 4. Restart the computer to ensure driver updates take effect.
🔧 Temporary Workarounds
Uninstall Advanced SystemCare Ultimate
windowsRemove the vulnerable software entirely to eliminate the attack surface
Control Panel > Programs > Uninstall a program > Select 'Advanced SystemCare Ultimate' > Uninstall
Restrict driver loading
windowsUse Group Policy or registry to restrict loading of unsigned or specific drivers
gpedit.msc > Computer Configuration > Windows Settings > Security Settings > System Services > Configure driver startup policies
🧯 If You Can't Patch
- Implement strict least privilege - ensure no users run with administrative rights unnecessarily
- Deploy endpoint detection and response (EDR) solutions to monitor for suspicious driver activity and privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check installed version of Advanced SystemCare Ultimate. If version is 14.2.0.220 or earlier, system is vulnerable.Check Version:
Open Advanced SystemCare Ultimate > Click 'About' or check Help > About menuVerify Fix Applied:
Verify Advanced SystemCare Ultimate version is 14.2.0.221 or later after update.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing driver loading events (Event ID 6, 219)
- Suspicious IOCTL requests to vulnerable driver
- Unexpected privilege escalation events
Network Indicators:
- Not applicable - local exploitation only
SIEM Query:
EventID=6 OR EventID=219 | where DriverName contains "Advanced SystemCare" OR ProcessName contains "ASCService"