CVE-2021-3146
📋 TL;DR
CVE-2021-3146 is a local privilege escalation vulnerability in Dolby Audio X2 (DAX2) API service on Windows. It allows local users to execute arbitrary code with SYSTEM privileges by exploiting improper permissions. This affects Windows systems with vulnerable DAX2 API service versions installed.
💻 Affected Systems
- Dolby Audio X2 (DAX2) API service
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Local attacker gains full SYSTEM privileges, enabling complete system compromise, data theft, persistence mechanisms, and lateral movement capabilities.
Likely Case
Local user or malware with initial access escalates to SYSTEM privileges to install additional malware, disable security controls, or access protected resources.
If Mitigated
With proper access controls and least privilege principles, impact is limited to the compromised user account without SYSTEM escalation.
🎯 Exploit Status
Exploitation requires local access but is straightforward once local access is obtained. The vulnerability involves improper permissions that allow local users to manipulate the service.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.8.8.90 or later
Vendor Advisory: https://professional.dolby.com/siteassets/pdfs/dolby-dax2-security-advisory-2021-04-07.pdf
Restart Required: Yes
Instructions:
1. Download DAX2 API service version 0.8.8.90 or later from Dolby. 2. Stop the DAX2 API service. 3. Install the updated version. 4. Restart the system to ensure changes take effect.
🔧 Temporary Workarounds
Disable DAX2 API Service
windowsStop and disable the vulnerable service if not required
sc stop "DAX2 API Service"
sc config "DAX2 API Service" start= disabled
Restrict Service Permissions
windowsModify service permissions to prevent unauthorized access
sc sdset "DAX2 API Service" D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWLOCRRC;;;IU)(A;;CCLCSWLOCRRC;;;SU)
🧯 If You Can't Patch
- Implement strict access controls to limit local user access to affected systems
- Monitor for suspicious service manipulation and privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check DAX2 API service version: Open Services (services.msc), find 'DAX2 API Service', check properties for version. If version is below 0.8.8.90, system is vulnerable.Check Version:
sc query "DAX2 API Service" | findstr /C:"DAX2 API Service"Verify Fix Applied:
Verify service version is 0.8.8.90 or higher and service is running normally without errors.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing service manipulation, unexpected service stops/starts, or privilege escalation attempts
Network Indicators:
- Local service communication anomalies, though primarily local exploitation
SIEM Query:
EventID=4688 AND (ProcessName LIKE '%dax2%' OR CommandLine LIKE '%dax2%') AND NewProcessName LIKE '%system%'