CVE-2021-30766
📋 TL;DR
This is a macOS kernel vulnerability that allows an application to write data beyond allocated memory boundaries. Successful exploitation could enable arbitrary code execution with kernel privileges, affecting macOS Big Sur, Catalina, and Mojave systems.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with kernel-level privileges, allowing attackers to install persistent malware, bypass security controls, and access all system resources.
Likely Case
Local privilege escalation where a malicious application gains kernel privileges to bypass sandboxing and security mechanisms.
If Mitigated
Limited impact if systems are patched, applications are from trusted sources, and security controls like Gatekeeper are enabled.
🎯 Exploit Status
Exploitation requires local application execution. No public exploit code has been disclosed as of knowledge cutoff.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Big Sur 11.5, Security Update 2021-004 Catalina, Security Update 2021-005 Mojave
Vendor Advisory: https://support.apple.com/en-us/HT212600
Restart Required: Yes
Instructions:
1. Open System Preferences > Software Update. 2. Install available security updates. 3. Restart the system when prompted.
🔧 Temporary Workarounds
Restrict application sources
macosConfigure Gatekeeper to only allow apps from the App Store and identified developers
sudo spctl --master-enable
sudo spctl --enable --label "Mac App Store"
sudo spctl --enable --label "Developer ID"
🧯 If You Can't Patch
- Restrict user privileges and limit application installations to trusted sources only
- Implement application allowlisting and monitor for suspicious process behavior
🔍 How to Verify
Check if Vulnerable:
Check macOS version: if running Big Sur < 11.5, Catalina without Security Update 2021-004, or Mojave without Security Update 2021-005Check Version:
sw_versVerify Fix Applied:
Verify macOS version meets patched requirements and check System Information for installed updates📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- Unexpected privilege escalation in audit logs
- Suspicious process creation with elevated privileges
Network Indicators:
- Unusual outbound connections from kernel processes
SIEM Query:
source="macos" AND (event_type="process_creation" AND parent_process="kernel_task") OR (event_type="privilege_escalation")