CVE-2021-30919
📋 TL;DR
This vulnerability allows arbitrary code execution through malicious PDF files due to an out-of-bounds write in Apple's PDF processing. It affects multiple Apple operating systems including iOS, iPadOS, macOS, tvOS, and watchOS. Attackers can exploit this by tricking users into opening specially crafted PDF documents.
💻 Affected Systems
- iOS
- iPadOS
- macOS
- tvOS
- watchOS
📦 What is this software?
Ipad Os by Apple
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 →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 with attacker gaining full control of the device, enabling data theft, surveillance, or ransomware deployment.
Likely Case
Targeted attacks against specific individuals or organizations using malicious PDF attachments or downloads leading to data exfiltration.
If Mitigated
No impact if systems are fully patched or if PDF processing is blocked through security controls.
🎯 Exploit Status
Exploitation requires user interaction to open malicious PDF but no authentication. No public proof-of-concept has been disclosed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: iOS 15.1, iPadOS 15.1, macOS Monterey 12.0.1, iOS 14.8.1, iPadOS 14.8.1, tvOS 15.1, watchOS 8.1, Security Update 2021-007 Catalina, macOS Big Sur 11.6.1
Vendor Advisory: https://support.apple.com/en-us/HT212867
Restart Required: Yes
Instructions:
1. Go to Settings > General > Software Update on iOS/iPadOS/watchOS. 2. Go to System Preferences > Software Update on macOS. 3. Install the latest available update. 4. Restart the device after installation.
🔧 Temporary Workarounds
Block PDF file processing
allUse endpoint protection or content filtering to block PDF files from untrusted sources.
Disable automatic PDF opening
allConfigure browsers and email clients to not automatically open PDF files.
🧯 If You Can't Patch
- Implement application allowlisting to prevent unauthorized PDF viewers
- Use network segmentation to isolate vulnerable devices from critical resources
🔍 How to Verify
Check if Vulnerable:
Check the operating system version against the affected versions listed in the Apple security advisories.Check Version:
iOS/iPadOS/watchOS: Settings > General > About > Version. macOS: Apple menu > About This Mac > macOS version.Verify Fix Applied:
Verify the device is running one of the patched versions: iOS 15.1+, iPadOS 15.1+, macOS Monterey 12.0.1+, iOS 14.8.1+, iPadOS 14.8.1+, tvOS 15.1+, watchOS 8.1+, or has Security Update 2021-007 Catalina/macOS Big Sur 11.6.1+.📡 Detection & Monitoring
Log Indicators:
- Unexpected process crashes related to PDF processing
- Unusual PDF file access from unexpected applications
Network Indicators:
- Downloads of PDF files from suspicious sources
- Outbound connections after PDF file opening
SIEM Query:
source="*" (event="process_crash" AND process_name="*pdf*") OR (file_type="pdf" AND source_ip="suspicious_ip")🔗 References
- https://support.apple.com/en-us/HT212867
- https://support.apple.com/en-us/HT212868
- https://support.apple.com/en-us/HT212869
- https://support.apple.com/en-us/HT212871
- https://support.apple.com/en-us/HT212872
- https://support.apple.com/en-us/HT212874
- https://support.apple.com/en-us/HT212876
- https://www.zerodayinitiative.com/advisories/ZDI-22-357/
- https://support.apple.com/en-us/HT212867
- https://support.apple.com/en-us/HT212868
- https://support.apple.com/en-us/HT212869
- https://support.apple.com/en-us/HT212871
- https://support.apple.com/en-us/HT212872
- https://support.apple.com/en-us/HT212874
- https://support.apple.com/en-us/HT212876
- https://www.zerodayinitiative.com/advisories/ZDI-22-357/
