CVE-2024-40821 – This CVE describes a sandbox escape vulnerabili... (How to Fix)

Q: What is the severity of CVE-2024-40821?

CVE-2024-40821 has a CVSS score of 7.1 (HIGH). This CVE describes a sandbox escape vulnerability in macOS where third-party app extensions may not receive proper sandbox restrictions. This could allow malicious extensions to bypass security boundaries and access restricted resources. Affected users are those running vulnerable macOS versions with third-party app extensions installed.

📋 TL;DR

This CVE describes a sandbox escape vulnerability in macOS where third-party app extensions may not receive proper sandbox restrictions. This could allow malicious extensions to bypass security boundaries and access restricted resources. Affected users are those running vulnerable macOS versions with third-party app extensions installed.

💻 Affected Systems

Products:

macOS

Versions: Versions prior to macOS Sonoma 14.6, macOS Monterey 12.7.6, macOS Ventura 13.6.8

Operating Systems: macOS

Default Config Vulnerable: ⚠️ Yes

Notes: Requires third-party app extensions to be installed. Apple's built-in extensions are not affected.

📦 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 →

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

A malicious app extension could escape sandbox restrictions, access sensitive user data, execute arbitrary code with elevated privileges, or perform unauthorized system modifications.

🟠

Likely Case

Malicious extensions could access files or resources they shouldn't be able to, potentially leading to data theft or privilege escalation within the user context.

🟢

If Mitigated

With proper macOS security controls and only trusted extensions installed, the impact is limited as the vulnerability requires malicious extensions to be present.

🌐 Internet-Facing: LOW - This vulnerability requires local access or user interaction to install malicious extensions, not directly exploitable over the internet.

🏢 Internal Only: MEDIUM - While it requires user interaction or malicious extensions, once exploited it could lead to significant privilege escalation within affected macOS systems.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires a user to install a malicious third-party app extension. No public exploit code has been disclosed as of the advisory dates.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: macOS Sonoma 14.6, macOS Monterey 12.7.6, macOS Ventura 13.6.8

Vendor Advisory: https://support.apple.com/en-us/HT214118

Restart Required: Yes

Instructions:

1. Open System Settings > General > Software Update. 2. Install the available macOS update. 3. Restart your Mac when prompted.

🔧 Temporary Workarounds

Disable Third-Party Extensions

macOS

Remove or disable third-party app extensions to eliminate the attack surface

Open System Settings > Privacy & Security > Extensions, then disable or remove third-party extensions

Restrict Extension Installation

macOS

Configure macOS to only allow extensions from trusted sources

Open System Settings > Privacy & Security > Security, set 'Allow apps downloaded from' to App Store or App Store and identified developers

🧯 If You Can't Patch

Only install app extensions from trusted, verified developers
Regularly audit installed extensions and remove any unnecessary or suspicious ones

🔍 How to Verify

Check if Vulnerable:

Check macOS version in System Settings > General > About. If version is earlier than Sonoma 14.6, Monterey 12.7.6, or Ventura 13.6.8, the system is vulnerable.

Check Version:

sw_vers

Verify Fix Applied:

After updating, verify macOS version shows Sonoma 14.6, Monterey 12.7.6, or Ventura 13.6.8 or later.

📡 Detection & Monitoring

Log Indicators:

Unusual extension activity in system logs
Sandbox violation logs
Unexpected file access by app extensions

Network Indicators:

Unusual outbound connections from app extension processes

SIEM Query:

source="macos_system_logs" AND (event="sandbox_violation" OR process="*extension*")

📊 Metadata

CVE ID: CVE-2024-40821

CVSS v3 Score: 7.1 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

CWE: CWE-281

Published: July 29, 2024

Last Updated: November 4, 2025

🔗 References

http://seclists.org/fulldisclosure/2024/Jul/18 Mailing List
http://seclists.org/fulldisclosure/2024/Jul/19 Mailing List
http://seclists.org/fulldisclosure/2024/Jul/20 Mailing List
https://support.apple.com/en-us/HT214118 Vendor Advisory
https://support.apple.com/en-us/HT214119 Vendor Advisory
https://support.apple.com/en-us/HT214120 Vendor Advisory
http://seclists.org/fulldisclosure/2024/Jul/18 Mailing List
http://seclists.org/fulldisclosure/2024/Jul/19 Mailing List
http://seclists.org/fulldisclosure/2024/Jul/20 Mailing List
https://support.apple.com/en-us/HT214118 Vendor Advisory
https://support.apple.com/en-us/HT214119 Vendor Advisory
https://support.apple.com/en-us/HT214120 Vendor Advisory
https://support.apple.com/kb/HT214118
https://support.apple.com/kb/HT214119
https://support.apple.com/kb/HT214120

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