CVE-2021-1772
📋 TL;DR
This vulnerability allows arbitrary code execution through a stack overflow when processing malicious text files. It affects macOS, iOS, iPadOS, tvOS, and watchOS users running outdated versions. Attackers can exploit this by tricking users into opening specially crafted text files.
💻 Affected Systems
- macOS
- iOS
- iPadOS
- tvOS
- watchOS
📦 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 privileges and persistent access to the device.
Likely Case
Local privilege escalation or remote code execution if combined with social engineering to deliver malicious files.
If Mitigated
Limited impact with proper file handling restrictions and user awareness training.
🎯 Exploit Status
Exploitation requires user interaction to open malicious files. No public exploit code is available, but the vulnerability is well-documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, watchOS 7.3, tvOS 14.4, iOS 14.4, iPadOS 14.4
Vendor Advisory: https://support.apple.com/en-us/HT212146
Restart Required: Yes
Instructions:
1. Open System Preferences > Software Update. 2. Install available updates. 3. Restart device when prompted. 4. Verify update installation in About This Mac or Settings.
🔧 Temporary Workarounds
Restrict text file handling
allConfigure systems to open text files in sandboxed applications only
User awareness training
allTrain users to avoid opening text files from untrusted sources
🧯 If You Can't Patch
- Implement application whitelisting to restrict which applications can open text files
- Deploy endpoint detection and response (EDR) solutions to monitor for suspicious file processing
🔍 How to Verify
Check if Vulnerable:
Check system version against affected versions list. On macOS: About This Mac > Overview. On iOS/iPadOS: Settings > General > About.Check Version:
macOS: sw_vers -productVersion; iOS/iPadOS: Settings > General > About > VersionVerify Fix Applied:
Verify system version matches or exceeds patched versions listed in fix_official section.📡 Detection & Monitoring
Log Indicators:
- Unusual process spawning from text editors or file handlers
- Stack overflow errors in system logs
- Unexpected file parsing activities
Network Indicators:
- Downloads of suspicious text files from untrusted sources
- Unusual outbound connections after file opening
SIEM Query:
process_name:("TextEdit" OR "Preview") AND event_type:process_start AND parent_process:user_interactive🔗 References
- https://support.apple.com/en-us/HT212146
- https://support.apple.com/en-us/HT212147
- https://support.apple.com/en-us/HT212148
- https://support.apple.com/en-us/HT212149
- https://www.zerodayinitiative.com/advisories/ZDI-21-758/
- https://support.apple.com/en-us/HT212146
- https://support.apple.com/en-us/HT212147
- https://support.apple.com/en-us/HT212148
- https://support.apple.com/en-us/HT212149
- https://www.zerodayinitiative.com/advisories/ZDI-21-758/
