CVE-2021-30829
📋 TL;DR
This CVE describes a URI parsing vulnerability in macOS that allows local users to execute arbitrary files. The issue affects macOS Catalina and Big Sur systems. Attackers could potentially run malicious code with the privileges of the current user.
💻 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
Local attacker gains full control of the system by executing arbitrary code with elevated privileges, potentially leading to complete system compromise.
Likely Case
Local user executes malicious files leading to data theft, privilege escalation, or persistence on the system.
If Mitigated
Attack limited to user-level access if proper application sandboxing and least privilege principles are enforced.
🎯 Exploit Status
Exploitation requires local access and user interaction. The vulnerability involves URI parsing issues that could be triggered through various macOS applications.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Security Update 2021-005 for macOS Catalina, macOS Big Sur 11.6
Vendor Advisory: https://support.apple.com/en-us/HT212804
Restart Required: Yes
Instructions:
1. Open System Preferences > Software Update. 2. Install Security Update 2021-005 (Catalina) or update to macOS Big Sur 11.6. 3. Restart the system when prompted.
🔧 Temporary Workarounds
Restrict local user access
allLimit local user accounts and implement strict access controls to reduce attack surface
🧯 If You Can't Patch
- Implement strict application control policies to limit which applications can be executed
- Use endpoint detection and response (EDR) solutions to monitor for suspicious file execution
🔍 How to Verify
Check if Vulnerable:
Check macOS version: 1. Click Apple menu > About This Mac. 2. If version is macOS Catalina (any version before Security Update 2021-005) or macOS Big Sur (any version before 11.6), system is vulnerable.Check Version:
sw_versVerify Fix Applied:
Verify macOS version is Security Update 2021-005 for Catalina or macOS Big Sur 11.6 or later in About This Mac.📡 Detection & Monitoring
Log Indicators:
- Unusual file execution events in Unified Logging System
- Suspicious process creation from URI handlers
Network Indicators:
- Not applicable - local vulnerability
SIEM Query:
source="macos" AND (event="process_creation" AND parent_process="launchservicesd") OR (event="file_access" AND file_path CONTAINS "file://")