CVE-2021-30949
📋 TL;DR
This CVE describes 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 complete control over 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 →Watchos by Apple
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with kernel-level privileges, allowing attackers to install persistent malware, bypass all security controls, access all data, and potentially create botnet nodes.
Likely Case
Malicious applications from untrusted sources exploiting the vulnerability to gain elevated privileges, install additional payloads, and maintain persistence on compromised devices.
If Mitigated
Limited impact with proper application sandboxing, code signing enforcement, and restricted app installation sources preventing malicious applications from reaching vulnerable systems.
🎯 Exploit Status
Exploitation requires a malicious application to be installed and executed on the target device. The vulnerability involves a use-after-free condition in mach_msg that can be leveraged for privilege escalation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Big Sur 11.6.2, macOS Monterey 12.1, Security Update 2021-008 Catalina, iOS 15.2, iPadOS 15.2, tvOS 15.2, watchOS 8.3
Vendor Advisory: https://support.apple.com/en-us/HT212975
Restart Required: Yes
Instructions:
1. Open System Preferences > Software Update on macOS or Settings > General > Software Update on iOS/iPadOS. 2. Install the available security update. 3. Restart the device when prompted.
🔧 Temporary Workarounds
Restrict Application Sources
allOnly allow installation of applications from trusted sources like the App Store to prevent malicious apps from exploiting the vulnerability.
For macOS: System Preferences > Security & Privacy > General > Allow apps downloaded from: App Store
For iOS/iPadOS: Settings > General > Device Management > Verify trusted sources
🧯 If You Can't Patch
- Implement strict application allowlisting to prevent unauthorized applications from executing
- Deploy endpoint detection and response (EDR) solutions to monitor for privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check the operating system version against the patched versions listed in the fix information.Check Version:
For macOS: sw_vers, For iOS/iPadOS: Settings > General > About > Version, For tvOS: Settings > General > About > Version, For watchOS: Watch app on iPhone > General > About > VersionVerify Fix Applied:
Verify the installed version matches or exceeds the patched versions: macOS Big Sur 11.6.2+, macOS Monterey 12.1+, iOS 15.2+, iPadOS 15.2+, tvOS 15.2+, watchOS 8.3+📡 Detection & Monitoring
Log Indicators:
- Unexpected kernel extensions loading
- Processes running with unexpected elevated privileges
- System integrity protection (SIP) violations
Network Indicators:
- Unusual outbound connections from system processes
- Command and control traffic from kernel-level processes
SIEM Query:
process_creation where parent_process_name contains "kernel" and process_name not in (approved_kernel_processes)🔗 References
- http://packetstormsecurity.com/files/165670/XNU-Kernel-mach_msg-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/165670/XNU-Kernel-mach_msg-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
