CVE-2021-31841
📋 TL;DR
A DLL sideloading vulnerability in McAfee Agent for Windows allows local users to execute arbitrary code with SYSTEM privileges by placing an unsigned DLL with a specific name in a specific location. This affects Windows systems running McAfee Agent versions prior to 5.7.4.
💻 Affected Systems
- McAfee Agent
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Local attacker gains SYSTEM privileges and full control of the Windows system, enabling installation of persistent malware, data theft, and lateral movement.
Likely Case
Local user or malware with initial access escalates privileges to SYSTEM to bypass security controls and maintain persistence.
If Mitigated
With proper patching and least privilege controls, impact is limited to denial of service or local user privilege escalation only.
🎯 Exploit Status
Exploitation requires local access and knowledge of specific DLL name and location. Public exploit details available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.7.4 or later
Vendor Advisory: https://kc.mcafee.com/corporate/index?page=content&id=SB10369
Restart Required: Yes
Instructions:
1. Download McAfee Agent 5.7.4 or later from McAfee support portal. 2. Deploy using ePolicy Orchestrator or manual installation. 3. Restart affected systems after installation.
🔧 Temporary Workarounds
Restrict DLL write permissions
windowsSet restrictive permissions on the vulnerable directory to prevent unauthorized DLL placement
icacls "C:\Program Files\McAfee\Agent\" /deny Users:(OI)(CI)W
Enable DLL signature verification
windowsConfigure Windows to require signed DLLs for McAfee processes
🧯 If You Can't Patch
- Implement strict file integrity monitoring on McAfee Agent directories
- Apply least privilege principles and restrict local user access to vulnerable systems
🔍 How to Verify
Check if Vulnerable:
Check McAfee Agent version via Control Panel > Programs and Features or command: Get-WmiObject -Class Win32_Product | Where-Object {$_.Name -like '*McAfee Agent*'} | Select-Object Name, VersionCheck Version:
Get-WmiObject -Class Win32_Product | Where-Object {$_.Name -like '*McAfee Agent*'} | Select-Object VersionVerify Fix Applied:
Verify version is 5.7.4 or higher using same command and check that DLL signature validation is enforced📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing DLL loading from unusual locations
- McAfee Agent logs showing unsigned DLL loading attempts
Network Indicators:
- Unusual outbound connections from McAfee Agent processes
SIEM Query:
EventID=4688 AND ProcessName LIKE '%McAfee%Agent%' AND CommandLine CONTAINS 'dll'