CVE-2021-1736
📋 TL;DR
This vulnerability allows attackers to execute arbitrary code by tricking users into processing maliciously crafted images. It affects macOS systems running vulnerable versions of Big Sur, Catalina, and Mojave. Successful exploitation could lead to full system compromise.
💻 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
Complete system takeover with attacker gaining root privileges and persistent access
Likely Case
Local privilege escalation or remote code execution when user opens malicious image file
If Mitigated
Limited impact if systems are patched and users avoid untrusted image files
🎯 Exploit Status
Exploitation requires user interaction to process malicious image, but technical details suggest reliable exploitation is possible
🛠️ 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 > Software Update 2. Install available security updates 3. Restart when prompted
🔧 Temporary Workarounds
Disable automatic image processing
allConfigure applications to not automatically process image files from untrusted sources
User education
allTrain users to avoid opening image files from unknown or untrusted sources
🧯 If You Can't Patch
- Implement application whitelisting to prevent execution of unauthorized applications
- Use network segmentation to isolate vulnerable systems and restrict file sharing
🔍 How to Verify
Check if Vulnerable:
Check macOS version in System Preferences > About This MacCheck Version:
sw_versVerify Fix Applied:
Verify macOS version is Big Sur 11.2 or later, or that Catalina/Mojave have Security Update 2021-001 installed📡 Detection & Monitoring
Log Indicators:
- Unusual process execution from image viewing applications
- Crash reports from image processing components
Network Indicators:
- Downloads of suspicious image files from external sources
SIEM Query:
Process creation events from image viewing applications with unusual parent processes or command line arguments