CVE-2021-30981
📋 TL;DR
This CVE-2021-30981 is a buffer overflow vulnerability in macOS that allows an application to execute arbitrary code with kernel privileges. It affects macOS Catalina, Big Sur, and Monterey before specific security updates. Attackers could gain full system control if they can run malicious code on the target system.
💻 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 privileges, allowing attackers to install persistent malware, steal all data, and control the entire operating system.
Likely Case
Local privilege escalation where a user or malware with standard user access gains kernel privileges to bypass security controls and install additional payloads.
If Mitigated
Limited impact if systems are fully patched, have application allowlisting, and users operate with least privilege.
🎯 Exploit Status
Exploitation requires local access or ability to execute code on the target system. No public proof-of-concept has been identified.
🛠️ 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 security updates. 3. Restart the system when prompted.
🔧 Temporary Workarounds
Application Control/Allowlisting
allImplement application allowlisting to prevent unauthorized applications from executing.
User Privilege Reduction
allEnsure users operate with standard privileges rather than administrative rights.
🧯 If You Can't Patch
- Isolate affected systems from critical networks and sensitive data
- Implement strict application control policies and monitor for suspicious process execution
🔍 How to Verify
Check if Vulnerable:
Check macOS version in System Preferences > About This Mac. If running Catalina, Big Sur, or Monterey without the specified security updates, the system is vulnerable.Check Version:
sw_versVerify Fix Applied:
Verify macOS version shows Monterey 12.1 or later, or that Security Update 2021-008 (Catalina) or 11.6.2 (Big Sur) is installed.📡 Detection & Monitoring
Log Indicators:
- Unusual kernel extensions loading
- Suspicious process privilege escalation
- Unauthorized application execution
Network Indicators:
- Outbound connections from kernel processes to suspicious destinations
SIEM Query:
Process creation events where parent process gains unexpected privileges or spawns from kernel space