CVE-2021-1858
📋 TL;DR
This vulnerability allows arbitrary code execution by processing a maliciously crafted image file. It affects Apple devices running outdated operating systems. Attackers can exploit this to gain control of affected systems.
💻 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
Full system compromise with attacker gaining root/admin privileges and persistent access
Likely Case
Local privilege escalation or remote code execution depending on attack vector
If Mitigated
No impact if systems are fully patched and image processing is restricted
🎯 Exploit Status
Exploitation requires user to process a malicious image, which could be delivered via email, messaging, or web
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Security Update 2021-002 Catalina, 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. For macOS, go to System Preferences > Software Update. 3. Install all available updates. 4. Restart device after installation.
🔧 Temporary Workarounds
Restrict image processing
allLimit image processing to trusted sources and disable automatic image loading
🧯 If You Can't Patch
- Implement application allowlisting to restrict which applications can process images
- Use network segmentation to isolate vulnerable systems and restrict internet access
🔍 How to Verify
Check if Vulnerable:
Check OS version against affected versions listCheck Version:
iOS/iPadOS: Settings > General > About > Version. macOS: Apple menu > About This Mac > macOS versionVerify Fix Applied:
Verify OS version is equal to or newer than patched versions listed📡 Detection & Monitoring
Log Indicators:
- Unexpected process crashes in image processing applications
- Unusual file access patterns for image files
Network Indicators:
- Unusual outbound connections from image processing applications
- Suspicious image file downloads
SIEM Query:
Process creation events from image processing applications followed by suspicious network connections🔗 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/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
