CVE-2021-34803
📋 TL;DR
This vulnerability in TeamViewer for Windows allows attackers to execute arbitrary code by placing malicious DLL files in specific directories that the application loads untrusted libraries from. It affects Windows users running TeamViewer versions before 14.7.48644, potentially enabling local privilege escalation or remote exploitation if combined with other weaknesses.
💻 Affected Systems
- TeamViewer
📦 What is this software?
Teamviewer by Teamviewer
Teamviewer by Teamviewer
Teamviewer by Teamviewer
Teamviewer by Teamviewer
Teamviewer by Teamviewer
Teamviewer by Teamviewer
Teamviewer by Teamviewer
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise via arbitrary code execution, leading to data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Local privilege escalation or limited code execution by an attacker with access to the system, potentially enabling further lateral movement.
If Mitigated
Minimal impact if patched or with strict file permissions preventing DLL planting; risk reduced to low with proper controls.
🎯 Exploit Status
Exploitation requires local access or ability to plant DLLs; no public proof-of-concept known, but DLL hijacking is a common technique.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 14.7.48644 or later
Vendor Advisory: https://community.teamviewer.com/English/discussion/111147/windows-v9-0-259145 (and related links)
Restart Required: Yes
Instructions:
1. Open TeamViewer. 2. Go to Help > Check for new version. 3. Follow prompts to update to version 14.7.48644 or newer. 4. Restart the application and system if required.
🔧 Temporary Workarounds
Restrict DLL loading paths
windowsSet strict file permissions on directories TeamViewer uses to prevent unauthorized DLL placement.
icacls "C:\Program Files (x86)\TeamViewer" /deny Everyone:(OI)(CI)(W)
Use application whitelisting
windowsConfigure Windows Defender Application Control or similar to allow only trusted DLLs.
🧯 If You Can't Patch
- Limit user permissions to prevent DLL planting in TeamViewer directories.
- Monitor for suspicious DLL creation or loading events using security tools.
🔍 How to Verify
Check if Vulnerable:
Check TeamViewer version in the application under Help > About; if below 14.7.48644, it is vulnerable.Check Version:
wmic product where name="TeamViewer" get versionVerify Fix Applied:
Confirm version is 14.7.48644 or higher in Help > About after update.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing DLL loading from unusual paths or failed integrity checks
Network Indicators:
- Unusual outbound connections from TeamViewer process post-exploitation
SIEM Query:
EventID=4688 AND ProcessName="TeamViewer.exe" AND CommandLine LIKE "%dll%"🔗 References
- https://community.teamviewer.com/English/discussion/111147/windows-v9-0-259145
- https://community.teamviewer.com/English/discussion/111149/windows-v10-0-259144
- https://community.teamviewer.com/English/discussion/111150/windows-v11-0-259143
- https://community.teamviewer.com/English/discussion/111151/windows-v12-0-259142
- https://community.teamviewer.com/English/discussion/111152/windows-v13-2-36222
- https://community.teamviewer.com/English/discussion/111153/windows-v14-2-56678
- https://community.teamviewer.com/English/discussion/111154/windows-v14-7-48644
- https://community.teamviewer.com/English/discussion/111147/windows-v9-0-259145
- https://community.teamviewer.com/English/discussion/111149/windows-v10-0-259144
- https://community.teamviewer.com/English/discussion/111150/windows-v11-0-259143
- https://community.teamviewer.com/English/discussion/111151/windows-v12-0-259142
- https://community.teamviewer.com/English/discussion/111152/windows-v13-2-36222
- https://community.teamviewer.com/English/discussion/111153/windows-v14-2-56678
- https://community.teamviewer.com/English/discussion/111154/windows-v14-7-48644
