CVE-2023-38602 - Understanding the macOS File System Permissions Flaw (And Why It Matters)

In July 2023, Apple patched a serious macOS security vulnerability tracked as CVE-2023-38602. This bug quietly hid in macOS Monterey, Ventura, and Big Sur, leaving protected parts of your system open for attack. If you’re using a Mac, or if you care about keeping computers safe, this is a big deal—especially for organizations and power users.

But what exactly is CVE-2023-38602? Why was it so dangerous? And how could an attacker exploit it? In this long read, we'll break it all down in simple terms, use sample code to show how attacks might work, and point you to original sources if you want to dig even deeper.

What is CVE-2023-38602?

CVE-2023-38602 is a permissions vulnerability in macOS. Because of this bug, a malicious app could write, change, or delete files in parts of the file system that Apple tries to protect—areas regular programs are not supposed to touch.

macOS Ventura 13.5

Apple's brief description:  
> "A permissions issue was addressed with additional restrictions. An app may be able to modify protected parts of the file system."

References:  
- Apple Security Updates: CVE-2023-38602
- NIST NVD Entry

Why Does It Matter?

macOS has special protections—like System Integrity Protection (SIP)—that stop apps, even ones running as root, from tampering with files and folders critical to the system. This keeps malware and sneaky apps from embedding themselves too deeply.

With CVE-2023-38602, those barriers could be skirted.

- A malicious or unwittingly installed app might quietly alter files in directories such as /System, /usr, or /Library.

How the Exploit Works (In Simple Terms)

Apple hasn’t published the exploit steps (for obvious security reasons), but security researchers and the National Vulnerability Database describe it generally:

*The vulnerability allowed apps that shouldn’t have a high level of access to gain write access to protected locations of the file system.*

Example Scenario

Let’s say an app is only sandboxed to write files to ~/Documents/, but because of this bug, it finds a way to modify something in /Library/LaunchDaemons/—where systemwide launch agents are stored.

The attacker creates a malicious launch agent file that would run on every boot.

2. Using the permissions bug, the app writes this file into /Library/LaunchDaemons/

Example Exploit Code Snippet

While the exact security bug is not public, we can illustrate what *shouldn’t* be possible, but *was* because of this vulnerability. Here’s an example in Python:

import os

malicious_daemon = '''
<?xml version="1." encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.//EN" "http://www.apple.com/DTDs/PropertyList-1..dtd">;
<plist version="1.">
<dict>
    <key>Label</key>
    <string>com.attacker.persistence</string>
    <key>ProgramArguments</key>
    <array>
        <string>/bin/bash</string>
        <string>-c</string>
        <string>echo "Malware runs with root!" >> /tmp/persist.txt</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
</dict>
</plist>
'''

# Path protected by SIP
path = '/Library/LaunchDaemons/com.attacker.persistence.plist'

# This should not succeed unless running as root or bypassing protections
try:
    with open(path, 'w') as f:
        f.write(malicious_daemon)
    print(f"[!] Launch Daemon written to: {path}")
except PermissionError as e:
    print("[!] Permission denied, as expected.")

Note: On a fully patched macOS, this script should fail unless run as root. The vulnerability allowed regular (unprivileged or sandboxed) processes to bypass this restriction.

Apple "addressed the permissions issue with additional restrictions." Simply put

- They tightened controls on what kinds of processes and apps can get through the system's file protections.
- They may have updated how path checks are done, or plugged a logic error in how file writes are handled under SIP.

Are You Vulnerable?

You may be, if:

Or macOS Ventura older than 13.5

How to check:

Conclusion

*CVE-2023-38602* is not something to shrug off. Its silent failure in macOS’s file system permissions could have been disastrous for users, businesses, and IT admins. Apple’s quick patch means the danger is over—if you update. Don’t leave your system open to attack through such a simple oversight.

References

- Apple Security Update July 2023
- National Vulnerability Database, CVE-2023-38602
- Apple’s System Integrity Protection (SIP) Guide

Timeline

Published on: 07/27/2023 01:15:38 UTC
Last modified on: 08/03/2023 04:28:29 UTC