CVE-2020-16853
📋 TL;DR
This CVE describes a privilege escalation vulnerability in OneDrive for Windows Desktop where improper handling of symbolic links allows an attacker to overwrite files with elevated privileges. Attackers must first log onto the system and run a specially crafted application. This affects Windows systems running vulnerable versions of OneDrive.
💻 Affected Systems
- OneDrive for Windows Desktop
📦 What is this software?
Onedrive by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
An attacker could delete or overwrite critical system files, potentially leading to system compromise, data loss, or persistence mechanisms.
Likely Case
Local attackers could escalate privileges to modify files they shouldn't have access to, potentially gaining higher privileges on the system.
If Mitigated
With proper patching, the vulnerability is eliminated. With proper access controls, the impact is limited to what the attacker's initial account can access.
🎯 Exploit Status
Exploitation requires local access, ability to log onto the system, and creation of a specially crafted application. Symbolic link manipulation is involved.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: OneDrive updates released in October 2020
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-16853
Restart Required: Yes
Instructions:
1. Open OneDrive settings. 2. Check for updates. 3. Install available updates. 4. Restart the system. 5. Verify OneDrive is running the latest version.
🔧 Temporary Workarounds
Disable OneDrive
windowsTemporarily disable OneDrive if patching is not immediately possible
Right-click OneDrive icon in system tray > Settings > Unlink this PC
🧯 If You Can't Patch
- Restrict local access to systems - ensure only authorized users can log onto affected machines
- Implement strict file permission controls to limit what users can access even if they exploit the vulnerability
🔍 How to Verify
Check if Vulnerable:
Check OneDrive version in settings. If version is from before October 2020, system is likely vulnerable.Check Version:
Check OneDrive settings > About tab for version informationVerify Fix Applied:
Verify OneDrive version is updated to post-October 2020 release and check Microsoft security advisory for confirmation.📡 Detection & Monitoring
Log Indicators:
- Unusual file modification events in system logs
- OneDrive process creating unexpected symbolic links
Network Indicators:
- No network indicators - this is a local privilege escalation
SIEM Query:
Process creation events for OneDrive.exe followed by file modification events with elevated privileges