CVE-2021-30856
📋 TL;DR
This macOS vulnerability allows malicious unsandboxed applications to bypass Privacy preferences when Remote Login is enabled. Attackers could gain unauthorized access to protected data. Affects macOS Big Sur systems with Remote Login enabled.
💻 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
Full system compromise with unauthorized access to all protected data including keychain, files, and system resources.
Likely Case
Unauthorized access to sensitive user data and system files that should be protected by Privacy preferences.
If Mitigated
Limited impact if Remote Login is disabled or proper application sandboxing is enforced.
🎯 Exploit Status
Requires local access with ability to run unsandboxed malicious application and Remote Login enabled.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Big Sur 11.3 and later
Vendor Advisory: https://support.apple.com/en-us/HT212325
Restart Required: Yes
Instructions:
1. Open System Preferences > Software Update. 2. Install macOS Big Sur 11.3 or later. 3. Restart the system when prompted.
🔧 Temporary Workarounds
Disable Remote Login
allTurn off Remote Login to prevent exploitation
sudo systemsetup -setremotelogin off
Enable Application Sandboxing
allEnsure all applications run with proper sandboxing
🧯 If You Can't Patch
- Disable Remote Login immediately via System Preferences > Sharing
- Implement strict application control policies to prevent unsandboxed apps
🔍 How to Verify
Check if Vulnerable:
Check macOS version with 'sw_vers' and verify Remote Login status with 'sudo systemsetup -getremotelogin'Check Version:
sw_versVerify Fix Applied:
Confirm macOS version is 11.3 or higher and check that Full Disk Access for SSH is properly configured📡 Detection & Monitoring
Log Indicators:
- Unauthorized SSH connection attempts
- Unexpected Full Disk Access requests
- System logs showing privacy preference bypass
Network Indicators:
- Unexpected SSH traffic from localhost
- SSH connections to unusual ports
SIEM Query:
source="system.log" AND ("Remote Login" OR "ssh" OR "privacy bypass")