CVE-2021-1843
📋 TL;DR
This vulnerability allows arbitrary code execution when processing maliciously crafted images on Apple devices. It affects multiple Apple operating systems including iOS, iPadOS, macOS, watchOS, and tvOS. Attackers could exploit this to run unauthorized code on affected devices.
💻 Affected Systems
- iOS
- iPadOS
- macOS
- watchOS
- tvOS
📦 What is this software?
Ipados by Apple
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 →Tvos by Apple
Watchos by Apple
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to execute arbitrary code with system privileges, potentially leading to data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Malicious image files delivered via email, messaging apps, or websites could trigger code execution, potentially compromising user data and device integrity.
If Mitigated
With proper patching, the vulnerability is eliminated. With network filtering and user education, risk is significantly reduced but not eliminated.
🎯 Exploit Status
Exploitation requires user interaction to open a malicious image file. No public exploit code is known, but the vulnerability is serious enough that weaponization is possible.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Security Update 2021-002 Catalina, Security Update 2021-003 Mojave, iOS 14.5, iPadOS 14.5, watchOS 7.4, tvOS 14.5, macOS Big Sur 11.3
Vendor Advisory: https://support.apple.com/en-us/HT212317
Restart Required: Yes
Instructions:
1. Go to Settings > General > Software Update on iOS/iPadOS/watchOS/tvOS. 2. Install available updates. 3. For macOS, go to System Preferences > Software Update. 4. Install all security updates. 5. Restart devices after installation.
🔧 Temporary Workarounds
Image Processing Restriction
allRestrict processing of untrusted image files through application controls or policies
Network Filtering
allBlock or scan image files from untrusted sources at network perimeter
🧯 If You Can't Patch
- Implement strict email filtering to block suspicious image attachments
- Educate users to avoid opening image files from untrusted sources
🔍 How to Verify
Check if Vulnerable:
Check current OS version against affected versions list. On macOS: About This Mac > Overview. On iOS/iPadOS: Settings > General > About > Version.Check Version:
macOS: sw_vers -productVersion; iOS/iPadOS: Settings > General > About > Version (no CLI command)Verify Fix Applied:
Verify OS version is equal to or newer than patched versions listed in fix_official section📡 Detection & Monitoring
Log Indicators:
- Unexpected process crashes in image processing applications
- Unusual file access patterns for image files
- Suspicious child processes spawned from image viewers
Network Indicators:
- Unusual outbound connections after image file processing
- Image file downloads from suspicious sources
SIEM Query:
Process creation events where parent process is an image viewer/editor and child process is unexpected (e.g., cmd.exe, bash, powershell)🔗 References
- https://support.apple.com/en-us/HT212317
- https://support.apple.com/en-us/HT212323
- https://support.apple.com/en-us/HT212324
- https://support.apple.com/en-us/HT212325
- https://support.apple.com/en-us/HT212326
- https://support.apple.com/en-us/HT212327
- https://support.apple.com/en-us/HT212317
- https://support.apple.com/en-us/HT212323
- https://support.apple.com/en-us/HT212324
- https://support.apple.com/en-us/HT212325
- https://support.apple.com/en-us/HT212326
- https://support.apple.com/en-us/HT212327
