CVE-2021-1790
📋 TL;DR
This vulnerability allows attackers to execute arbitrary code by tricking users into processing malicious font files. It affects macOS systems running older versions that haven't applied Apple's security updates. Successful exploitation could give attackers full control of the affected system.
💻 Affected Systems
- macOS
📦 What is this software?
Macos by Apple
macOS is Apple's desktop and laptop operating system powering Mac computers used by millions of professionals, developers, creative professionals, and enterprise users worldwide. Built on a Unix foundation with the Darwin kernel and modern Cocoa frameworks, macOS delivers a seamless ecosystem integr...
Learn more about Macos →⚠️ Risk & Real-World Impact
Worst Case
Full system compromise leading to data theft, ransomware deployment, or persistent backdoor installation
Likely Case
Malware installation through phishing emails or malicious websites containing crafted fonts
If Mitigated
Limited impact if systems are patched and users avoid suspicious font files
🎯 Exploit Status
Exploitation requires user interaction to process malicious font files
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave
Vendor Advisory: https://support.apple.com/en-us/HT212147
Restart Required: Yes
Instructions:
1. Open System Preferences 2. Click Software Update 3. Install available security updates 4. Restart when prompted
🔧 Temporary Workarounds
Restrict font processing
allBlock suspicious font files at network perimeter and educate users about font file risks
🧯 If You Can't Patch
- Implement application whitelisting to prevent unauthorized code execution
- Use network segmentation to isolate vulnerable systems from critical assets
🔍 How to Verify
Check if Vulnerable:
Check macOS version in About This Mac. If version is earlier than Big Sur 11.2, Catalina Security Update 2021-001, or Mojave Security Update 2021-001, system is vulnerableCheck Version:
sw_versVerify Fix Applied:
Verify macOS version shows patched version in About This Mac📡 Detection & Monitoring
Log Indicators:
- Unusual font processing activity, unexpected application launches after font file access
Network Indicators:
- Downloads of suspicious font files from untrusted sources
SIEM Query:
process:launch AND file_extension:ttf OR file_extension:otf OR file_extension:fon