CVE-2020-3915
📋 TL;DR
CVE-2020-3915 is a path handling vulnerability in macOS that allows malicious applications to overwrite arbitrary files on the system. This affects macOS Catalina versions prior to 10.15.4. The vulnerability requires user interaction to install or run a malicious application.
💻 Affected Systems
- macOS
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through overwriting critical system files, privilege escalation, or persistent backdoor installation.
Likely Case
Data destruction, configuration file tampering, or installation of additional malware payloads.
If Mitigated
Limited impact if application sandboxing and file system permissions are properly configured.
🎯 Exploit Status
Requires user interaction to install malicious application. No known public exploits.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Catalina 10.15.4 or later
Vendor Advisory: https://support.apple.com/kb/HT211100
Restart Required: Yes
Instructions:
1. Open System Preferences 2. Click Software Update 3. Install macOS Catalina 10.15.4 or later update 4. Restart when prompted
🔧 Temporary Workarounds
Restrict application installation
macOSLimit application installation to App Store only or require administrator approval
Enable Gatekeeper
macOSEnsure Gatekeeper is enabled to block unsigned applications
sudo spctl --master-enable
🧯 If You Can't Patch
- Implement application allowlisting to prevent unauthorized applications
- Use endpoint protection with behavioral analysis to detect malicious file operations
🔍 How to Verify
Check if Vulnerable:
Check macOS version: if running Catalina and version is less than 10.15.4, system is vulnerableCheck Version:
sw_versVerify Fix Applied:
Verify macOS version is 10.15.4 or later📡 Detection & Monitoring
Log Indicators:
- Unusual file write operations by applications, especially to system directories
Network Indicators:
- Downloads of suspicious applications from untrusted sources
SIEM Query:
process:write AND target_path:/System/* OR target_path:/etc/* OR target_path:/usr/*