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CVE-2021-30924

7.5 HIGH
Denial of Service

📋 TL;DR

This CVE describes a denial-of-service vulnerability in macOS that allows a remote attacker to cause affected devices to unexpectedly restart. The issue was fixed in macOS Monterey 12.0.1. All macOS systems running vulnerable versions are affected.

💻 Affected Systems

Products:
  • macOS
Versions: Versions prior to macOS Monterey 12.0.1
Operating Systems: macOS
Default Config Vulnerable: ⚠️ Yes
Notes: All default configurations of affected macOS versions are vulnerable. No special configuration required for exploitation.

📦 What is this software?

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Macos by Apple

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⚠️ Risk & Real-World Impact

🔴

Worst Case

Persistent denial-of-service attacks causing repeated system restarts, disrupting business operations and potentially causing data loss or corruption.

🟠

Likely Case

Temporary service disruption with system restart, causing downtime for affected devices.

🟢

If Mitigated

Minimal impact with proper network segmentation and updated systems.

🌐 Internet-Facing: HIGH - Remote attackers can exploit this without authentication, making internet-facing systems particularly vulnerable.
🏢 Internal Only: MEDIUM - Internal systems are still vulnerable but require attacker presence on the network.

🎯 Exploit Status

Public PoC: ✅ No
Weaponized: UNKNOWN
Unauthenticated Exploit: ⚠️ Yes
Complexity: LOW

Apple's description indicates remote exploitation is possible without authentication, suggesting relatively straightforward exploitation.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: macOS Monterey 12.0.1

Vendor Advisory: https://support.apple.com/en-us/HT212869

Restart Required: Yes

Instructions:

1. Open System Preferences > Software Update. 2. Install macOS Monterey 12.0.1 update. 3. Restart the system when prompted.

🔧 Temporary Workarounds

Network Segmentation

all

Restrict network access to vulnerable macOS systems to trusted networks only.

Firewall Rules

all

Implement strict firewall rules to limit inbound connections to vulnerable systems.

🧯 If You Can't Patch

  • Isolate vulnerable systems from untrusted networks and internet access.
  • Implement network monitoring for unusual restart patterns or denial-of-service attempts.

🔍 How to Verify

Check if Vulnerable:

Check macOS version: if running macOS Monterey earlier than 12.0.1, the system is vulnerable.

Check Version:

sw_vers

Verify Fix Applied:

Verify macOS version is 12.0.1 or later via System Information or terminal command.

📡 Detection & Monitoring

Log Indicators:

  • Unexpected system restarts in system logs
  • Kernel panic logs
  • Crash reports indicating abnormal termination

Network Indicators:

  • Unusual network traffic patterns preceding system restarts
  • Multiple connection attempts from single sources

SIEM Query:

source="macos_system_logs" AND (event="restart" OR event="shutdown") AND NOT user="root" AND NOT process="softwareupdated"

📊 Metadata

CVE ID: CVE-2021-30924
CVSS v3 Score: 7.5 (HIGH)
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: August 24, 2021
Last Updated: November 21, 2024

🔗 References

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