In early 2024, Apple quietly patched a logic flaw—tracked as CVE-2024-27789—that potentially let malicious apps break the walls and snoop on user-sensitive data on iPhones, iPads, and Macs. This issue didn’t make front-page headlines, but it’s a great reminder of why software updates are critical, and how even small programming errors can put your info at risk.

In this post, we’ll break down what happened, show a simplified code example, offer links for further reading, and explain what you should do now.

Official description

> "A logic issue was addressed with improved checks. This issue is fixed in iOS 16.7.8 and iPadOS 16.7.8, macOS Monterey 12.7.5, macOS Ventura 13.6.7, macOS Sonoma 14.4. An app may be able to access user-sensitive data."

Source: Apple Security Updates - CVE-2024-27789

Put simply, a bug in the decision-making code could let a rogue app bypass some restrictions and peek at things it should not see—think private files, account info, or even user messages (depending on the app and device).

How Did This Happen? (Explained Simply)

Somewhere in Apple’s code was a set of rules checking if an app had permission to access certain data. Because of a "logic issue," these checks didn’t always work as they should. That meant apps could slip through security gates under special conditions.

Imagine a security guard checking tickets at a theater, but someone with a cleverly forged ticket gets in because the guard sometimes looked at the wrong part of the ticket. That’s a logic bug.

Let’s say you have this simplified Swift code in some service

func canAccessSensitiveData(app: App) -> Bool {
    if app.isSandboxed {
        return false
    }
    // ...other rules...
    return true
}

Suppose isSandboxed isn’t reliable (maybe because of an unexpected app state), or maybe a logical mistake like using || (OR) instead of && (AND):

func canAccessSensitiveData(app: App) -> Bool {
    // LOGIC BUG: should be && instead of ||
    if app.hasUserConsent || app.isWhitelisted {
        return true
    }
    return false
}

With the OR (||), either condition being true allows access; if that isn’t the intended policy, it’s a problem! An app with user consent for _any_ data or with a loophole in the whitelist might get access.

Exploit Details (How Would Attackers Abuse This?)

Before the patch, a malicious app could create conditions (maybe by tricking the system about its state or permissions) so Apple’s checks would pass—even though the app wasn’t supposed to access user data. The app could then grab personal files, credentials, or other sensitive materials.

No public exploit has been released, but this sort of bug is often used in

- Malicious apps on the App Store (or via sideloading/testflight)

How Did Apple Fix It?

The update rounded out the flawed logic, rewriting the code to handle all cases correctly. The official note is: "A logic issue was addressed with improved checks." This likely means:

Adding extra validation steps

If you update your device, you’re protected against CVE-2024-27789.

macOS Sonoma 14.4 or later

you’re safe from this bug. If not, update ASAP.

References & Further Reading

- Apple Security Updates - CVE-2024-27789
- NIST NVD Entry for CVE-2024-27789
- MacRumors: iOS 16.7.8 and Security Fixes

Bottom Line

CVE-2024-27789 is a textbook example of why even mature platforms like iOS and macOS need constant review. Little mistakes in logic can lead to big privacy risks. Update your devices, stay alert to security news, and always keep only trusted apps installed.

Have more questions, or curious about other vulnerabilities? Drop them in the comments—security is everyone’s business!

Timeline

Published on: 05/14/2024 15:13:01 UTC
Last modified on: 11/15/2024 22:35:08 UTC