CVE-2021-1687
📋 TL;DR
CVE-2021-1687 is an elevation of privilege vulnerability in Windows WalletService that allows authenticated attackers to execute arbitrary code with SYSTEM privileges. This affects Windows 10 and Windows Server systems where WalletService is enabled. Attackers must have valid credentials and local access to exploit this vulnerability.
💻 Affected Systems
- Windows 10
- Windows Server 2016
- Windows Server 2019
- Windows Server 2022
📦 What is this software?
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
An authenticated attacker gains SYSTEM privileges, enabling complete system compromise, data theft, persistence establishment, and lateral movement across the network.
Likely Case
Malicious insiders or attackers with stolen credentials escalate privileges to install malware, steal sensitive data, or maintain persistence on compromised systems.
If Mitigated
With proper access controls, patch management, and credential hygiene, exploitation is limited to authorized users who would already have legitimate access.
🎯 Exploit Status
Exploitation requires local access and valid user credentials. Public proof-of-concept code exists, making exploitation straightforward for attackers with initial access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Security updates released in January 2021 (KB4598242, KB4598229, etc.)
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1687
Restart Required: Yes
Instructions:
1. Apply the January 2021 Windows security updates. 2. Restart the system. 3. Verify the update is installed via Windows Update history or system information.
🔧 Temporary Workarounds
Disable WalletService
windowsDisables the vulnerable WalletService component to prevent exploitation
sc config WalletService start= disabled
sc stop WalletService
🧯 If You Can't Patch
- Implement strict access controls and credential hygiene to limit potential attackers
- Monitor for privilege escalation attempts and unusual WalletService activity
🔍 How to Verify
Check if Vulnerable:
Check if January 2021 security updates are installed via 'systeminfo' or Windows Update historyCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify KB4598242 (or relevant update) is installed and WalletService version is updated📡 Detection & Monitoring
Log Indicators:
- Unusual WalletService process creation
- Privilege escalation attempts
- Suspicious service manipulation
Network Indicators:
- Lateral movement from compromised systems
- Unusual authentication patterns
SIEM Query:
EventID=4688 AND ProcessName="WalletService.exe" AND NewProcessName contains "cmd.exe" OR "powershell.exe"