CVE-2021-30977
📋 TL;DR
This CVE describes a buffer overflow vulnerability in macOS that allows malicious applications to execute arbitrary code with kernel privileges. It affects macOS Catalina, Big Sur, and Monterey before specific security updates. Users running unpatched versions of these macOS releases are vulnerable.
💻 Affected Systems
- macOS
📦 What is this software?
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 →⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with kernel-level access, allowing attackers to install persistent malware, steal sensitive data, or disable security controls.
Likely Case
Malicious applications exploiting this to gain elevated privileges, potentially leading to data theft or system manipulation.
If Mitigated
Limited impact if proper application sandboxing and least privilege principles are enforced, though kernel access remains dangerous.
🎯 Exploit Status
Exploitation requires user to run a malicious application; no known public exploits as of analysis.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Monterey 12.1, Security Update 2021-008 Catalina, macOS Big Sur 11.6.2
Vendor Advisory: https://support.apple.com/en-us/HT212978
Restart Required: Yes
Instructions:
1. Open System Preferences > Software Update. 2. Install available updates. 3. Restart when prompted.
🔧 Temporary Workarounds
Application Restriction
macOSRestrict installation and execution of untrusted applications
sudo spctl --master-enable
sudo spctl --enable
🧯 If You Can't Patch
- Implement strict application control policies to prevent execution of untrusted applications
- Use endpoint detection and response (EDR) tools to monitor for suspicious kernel activity
🔍 How to Verify
Check if Vulnerable:
Check macOS version in System Preferences > About This MacCheck Version:
sw_versVerify Fix Applied:
Verify macOS version matches patched versions: Monterey 12.1+, Catalina with Security Update 2021-008, Big Sur 11.6.2+📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- Unexpected kernel module loading
- Suspicious process privilege escalation
Network Indicators:
- None - local exploitation only
SIEM Query:
process where parent_process_name contains "kernel" and process_name not in (approved_kernel_processes)🔗 References
- https://support.apple.com/en-us/HT212978
- https://support.apple.com/en-us/HT212979
- https://support.apple.com/en-us/HT212981
- https://support.apple.com/kb/HT213183
- https://support.apple.com/en-us/HT212978
- https://support.apple.com/en-us/HT212979
- https://support.apple.com/en-us/HT212981
- https://support.apple.com/kb/HT213183
