CVE-2024-7227
📋 TL;DR
This vulnerability in Avast Free Antivirus allows local attackers to escalate privileges to SYSTEM level by exploiting a symbolic link issue in the Avast Service. Attackers must first gain low-privileged code execution on the target system. Only Avast Free Antivirus installations are affected.
💻 Affected Systems
- Avast Free Antivirus
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full SYSTEM privilege compromise leading to complete system takeover, data theft, malware persistence, and lateral movement across the network.
Likely Case
Local privilege escalation from a standard user account to SYSTEM, enabling installation of malware, disabling security controls, and accessing protected system resources.
If Mitigated
Limited impact if proper endpoint protection, least privilege principles, and application whitelisting are enforced to prevent initial low-privileged code execution.
🎯 Exploit Status
Exploitation requires local access and ability to create symbolic links; ZDI has confirmed the vulnerability but no public exploit is available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in available references; check latest Avast updates
Vendor Advisory: https://www.avast.com/en-us/support
Restart Required: Yes
Instructions:
1. Open Avast Free Antivirus. 2. Navigate to Settings > Update > Virus Definitions. 3. Click 'Update' to ensure latest definitions. 4. Check for program updates in Settings > General > Update. 5. Restart the system after updates are applied.
🔧 Temporary Workarounds
Disable Avast Service Temporarily
windowsTemporarily stops the vulnerable service to prevent exploitation (impacts antivirus functionality)
sc stop AvastSvc
sc config AvastSvc start= disabled
Restrict Symbolic Link Creation
windowsConfigure Windows to restrict who can create symbolic links (requires administrative privileges)
secedit /export /cfg config.inf
Edit config.inf to set 'Create symbolic links' to Administrators only
secedit /configure /db config.sdb /cfg config.inf
🧯 If You Can't Patch
- Implement strict least privilege principles to prevent initial low-privileged code execution
- Deploy application control/whitelisting to block unauthorized processes from running
🔍 How to Verify
Check if Vulnerable:
Check Avast version and ensure it's updated to latest; vulnerability exists if AvastSvc is running on unpatched versions.Check Version:
"C:\Program Files\Avast Software\Avast\AvastUI.exe" /? or check in Avast UI under Settings > AboutVerify Fix Applied:
Verify Avast is updated to latest version and no security alerts indicate privilege escalation attempts.📡 Detection & Monitoring
Log Indicators:
- Windows Security Event ID 4688 for AvastSvc process creation with unusual parent
- Symbolic link creation events in Windows logs
- Unexpected file deletion attempts via Avast processes
Network Indicators:
- No specific network indicators as this is local exploitation
SIEM Query:
EventID=4688 AND ProcessName="AvastSvc.exe" AND ParentProcessName NOT IN ("services.exe", "svchost.exe")