CVE-2021-30937
📋 TL;DR
This is a memory corruption vulnerability in Apple's XNU kernel that allows a malicious application to execute arbitrary code with kernel privileges. It affects multiple Apple operating systems including macOS, iOS, iPadOS, tvOS, and watchOS. Attackers could gain full control of affected devices.
💻 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 →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 kernel-level code execution, allowing attackers to install persistent malware, steal sensitive data, or disable security controls.
Likely Case
Malicious apps from untrusted sources exploiting the vulnerability to gain elevated privileges and perform unauthorized actions on the device.
If Mitigated
Limited impact if devices are updated to patched versions and only trusted applications are installed from official sources.
🎯 Exploit Status
Exploitation requires a malicious application to be run locally; public proof-of-concept details heap use-after-free in XNU's inm_merge function.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Big Sur 11.6.2, tvOS 15.2, macOS Monterey 12.1, Security Update 2021-008 Catalina, iOS 15.2 and iPadOS 15.2, watchOS 8.3
Vendor Advisory: https://support.apple.com/en-us/HT212975
Restart Required: Yes
Instructions:
1. Go to System Preferences > Software Update on macOS or Settings > General > Software Update on iOS/iPadOS/tvOS/watchOS. 2. Install the available update. 3. Restart the device as prompted.
🔧 Temporary Workarounds
Restrict application installation
allOnly allow installation of applications from trusted sources like the App Store to reduce risk of malicious apps.
🧯 If You Can't Patch
- Isolate affected devices on network segments to limit lateral movement if compromised.
- Implement application allowlisting to prevent execution of untrusted applications.
🔍 How to Verify
Check if Vulnerable:
Check the operating system version against the affected versions listed in the Apple security advisories.Check Version:
On macOS: 'sw_vers -productVersion'. On iOS/iPadOS: Go to Settings > General > About > Version. On tvOS: Settings > General > About > Version. On watchOS: Open Watch app on iPhone > General > About > Version.Verify Fix Applied:
Verify that the device is running one of the patched versions specified in the fix information.📡 Detection & Monitoring
Log Indicators:
- Unusual kernel panic logs or crashes, unexpected privilege escalation events in system logs.
Network Indicators:
- Unusual outbound connections from system processes post-exploitation.
SIEM Query:
Search for events indicating kernel-level anomalies or unauthorized privilege changes on Apple devices.🔗 References
- http://packetstormsecurity.com/files/165475/XNU-inm_merge-Heap-Use-After-Free.html
- https://support.apple.com/en-us/HT212975
- https://support.apple.com/en-us/HT212976
- https://support.apple.com/en-us/HT212978
- https://support.apple.com/en-us/HT212979
- https://support.apple.com/en-us/HT212980
- https://support.apple.com/en-us/HT212981
- http://packetstormsecurity.com/files/165475/XNU-inm_merge-Heap-Use-After-Free.html
- https://support.apple.com/en-us/HT212975
- https://support.apple.com/en-us/HT212976
- https://support.apple.com/en-us/HT212978
- https://support.apple.com/en-us/HT212979
- https://support.apple.com/en-us/HT212980
- https://support.apple.com/en-us/HT212981
