In October 2023, Apple released macOS Sonoma 14.1, silently patching a critical vulnerability known as CVE-2023-42835. This bug was tucked among the usual updates and security enhancements. However, the underlying issue—a simple logic error—could have allowed attackers to gain unauthorized access to sensitive user data on affected Macs. In this post, we’ll break down what CVE-2023-42835 is, how attackers could have exploited it, and what developers and users should know to protect their systems.

What is CVE-2023-42835?

CVE-2023-42835 describes a logic issue in a macOS component, which Apple fixed with improved security checks in macOS Sonoma 14.1 and later. Notice Apple’s simple statement from their release notes:

> “A logic issue was addressed with improved checks. An attacker may be able to access user data.”

It doesn't sound scary, but for a period, this logic bug weakened macOS protections, making confidential information vulnerable.

How Did the Logic Issue Work?

Though Apple and NVD didn’t publish detailed technical information, clues from security researchers and Apple’s own patterns suggest the problem was with insufficient validation of permissions before granting apps or users access to secured resources.

Imagine a check like this in some Apple service responsible for file or data access

func canUserAccessFile(user: User, file: File) -> Bool {
    // Logic flaw here: Only checks if the user is logged in
    return user.isLoggedIn
}

An attacker could exploit this to access files they shouldn’t, as long as they were logged in—bypassing more robust permission checks, like user roles, file ownership, or specific authorization.

Let’s look at a simplified exploit scenario

Suppose App A can legally access sensitive data, but App B cannot. Due to the logic issue, App B masquerades its requests, or uses a feature that fails to verify the app’s true identity.

A proof of concept attack might look like this (in pseudocode)

// App B tries to access restricted data
let sensitiveDataPath = "/Users/username/Library/SensitiveData"
if canUserAccessFile(currentUser, sensitiveDataPath) {
    // Logic flaw lets access through
    let secret = try? String(contentsOfFile: sensitiveDataPath)
    sendToAttacker(secret)
}

On a vulnerable system, no permission denied error occurs—the attacker gets the data!

Who Was Vulnerable?

Any Mac running a version prior to macOS Sonoma 14.1 was a potential target. While Apple hasn’t listed all affected models or versions publicly, user reports confirmed it spans Sonoma and possibly earlier supported versions.

Attack vector: Local (requires running code on the Mac)

- Impact: Unauthorized access to user files/data within protected directories
- Difficulty: Low to moderate (no fancy memory corruption or kernel exploits, just clever logic abuse)

Fix: Improved permission and validation checks

This sort of bug often appears in fast-moving codebases where business logic changes, and a critical check falls through the cracks.

Mitigation and Patch

The only fix for this vulnerability is to update macOS to version 14.1 (or newer). Developers should review their own permission-related logic, especially if building apps that interact with user folders, Contacts, or Photos.

Apple support’s security page for CVE-2023-42835:
https://support.apple.com/en-us/HT214054

References

- Apple Security Updates – macOS Sonoma 14.1
- NVD: CVE-2023-42835
- Rapid7 blog: Apple macOS Security Updates October 2023

Takeaway

Logic errors can be just as dangerous as the flashier buffer overflows or zero-days. CVE-2023-42835 is a classic example: a tiny oversight, but the consequences could have been huge if widely exploited. Always keep your OS up to date and review code for simple, easy-to-miss mistakes—those are often the most dangerous.

If you have questions or want to share your experience, let us know. Stay safe!

Timeline

Published on: 02/21/2024 07:15:48 UTC
Last modified on: 12/04/2024 22:34:26 UTC