CVE-2021-24083
📋 TL;DR
CVE-2021-24083 is a remote code execution vulnerability in Windows Address Book that allows attackers to execute arbitrary code on affected systems. It affects Windows clients and servers when they process specially crafted files. Attackers could exploit this by tricking users into opening malicious files or visiting compromised websites.
💻 Affected Systems
- Microsoft Windows
📦 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
Windows 7 by Microsoft
Windows 8.1 by Microsoft
Windows Rt 8.1 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining SYSTEM privileges, enabling data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Limited user-level compromise leading to credential theft, lateral movement within networks, or installation of malware on individual systems.
If Mitigated
No impact if systems are patched, users avoid untrusted files, and proper endpoint protection blocks malicious content.
🎯 Exploit Status
Exploitation requires user interaction to open malicious files. Proof-of-concept code has been published, making weaponization likely.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: February 2021 security updates (KB4601319 for Windows 10 20H2, KB4601345 for Windows Server 2019, etc.)
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-24083
Restart Required: Yes
Instructions:
1. Apply February 2021 Windows security updates via Windows Update. 2. For enterprise environments, deploy updates through WSUS or SCCM. 3. Restart systems after update installation.
🔧 Temporary Workarounds
Disable Windows Address Book Protocol Handler
windowsPrevents Windows from handling WAB files that could trigger the vulnerability
reg add "HKLM\SOFTWARE\Classes\wab\shell\open\command" /ve /d "" /f
Block WAB File Extensions
allPrevents execution of Windows Address Book files at the network perimeter
🧯 If You Can't Patch
- Implement application whitelisting to prevent execution of unauthorized applications
- Deploy endpoint detection and response (EDR) solutions to detect and block malicious file execution
🔍 How to Verify
Check if Vulnerable:
Check Windows version and update status. Systems without February 2021 security updates are vulnerable.Check Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify that February 2021 security updates (KB4601319, KB4601345, or equivalent) are installed via 'winver' or 'systeminfo' command.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing unexpected WAB file execution
- Security logs with process creation events from wab.exe with suspicious parameters
Network Indicators:
- Unusual outbound connections from systems after WAB file execution
- Downloads of WAB files from untrusted sources
SIEM Query:
Process Creation where (ImagePath contains "wab.exe" AND CommandLine contains suspicious patterns)