CVE-2021-30739
📋 TL;DR
CVE-2021-30739 is a local privilege escalation vulnerability in macOS caused by a memory corruption issue. A local attacker could exploit this to gain elevated privileges on affected systems. This affects macOS Big Sur, Catalina, and Mojave versions before the security updates.
💻 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
An attacker with local access could gain root privileges, potentially taking full control of the system, accessing sensitive data, installing persistent malware, or pivoting to other systems.
Likely Case
A local user or malware could elevate privileges to install additional malicious software, modify system configurations, or access protected files and resources.
If Mitigated
With proper access controls and least privilege principles, the impact is limited to the specific compromised user account rather than full system compromise.
🎯 Exploit Status
Exploitation requires local access and knowledge of the memory corruption vulnerability. Apple has not disclosed technical details to prevent exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Big Sur 11.4, Security Update 2021-003 Catalina, Security Update 2021-004 Mojave
Vendor Advisory: https://support.apple.com/en-us/HT212529
Restart Required: Yes
Instructions:
1. Open System Preferences > Software Update. 2. Install available security updates. 3. Restart the system when prompted. 4. Verify the update completed successfully.
🔧 Temporary Workarounds
Restrict local access
allLimit physical and remote local access to vulnerable systems to reduce attack surface
Implement least privilege
allEnsure users operate with minimal necessary privileges to limit impact if exploited
🧯 If You Can't Patch
- Implement strict access controls to limit who has local access to vulnerable systems
- Monitor for suspicious privilege escalation attempts and unauthorized system modifications
🔍 How to Verify
Check if Vulnerable:
Check macOS version: 1. Click Apple menu > About This Mac. 2. If version is earlier than Big Sur 11.4, Catalina with Security Update 2021-003, or Mojave with Security Update 2021-004, system is vulnerable.Check Version:
sw_versVerify Fix Applied:
1. Click Apple menu > About This Mac. 2. Verify version is Big Sur 11.4 or later, or Catalina/Mojave with the specified security updates installed.📡 Detection & Monitoring
Log Indicators:
- Unexpected privilege escalation events in system logs
- Unauthorized sudo or root access attempts
- Unusual process creation with elevated privileges
Network Indicators:
- Local privilege escalation typically doesn't generate network traffic unless attacker pivots
SIEM Query:
source="macos_system_logs" AND (event="privilege_escalation" OR process="sudo" OR user="root") AND NOT expected_pattern