Apple’s software is famous for its dedication to privacy and security. However, no system is perfect. In October 2023, a security hole identified as CVE-2023-42839 made headlines for putting sensitive user data at risk across multiple Apple devices. This post breaks down CVE-2023-42839 in plain English, explains how attackers might have exploited it, and shows how Apple addressed the issue.

What is CVE-2023-42839?

CVE-2023-42839 is a vulnerability found in Apple’s tvOS, watchOS, macOS Sonoma, iOS, and iPadOS. Essentially, a rogue app could have sidestepped Apple’s privacy guardrails to access sensitive user data it shouldn’t have been able to reach.

According to Apple’s official security notes

> "An app may be able to access sensitive user data. This issue was addressed with improved state management."

Calendar entries

A vulnerable app could have reached into these private silos without your explicit permission, which is a major privacy breach.

How Could This Have Happened?

The technical description is vague (“improved state management”), but based on similar bugs and Apple’s previous fixes, we can illustrate a likely scenario.

Suppose apps on iOS, for instance, use what’s called sandboxing, which keeps each app locked to its own private data. Apps can only access sensitive information if you – the user – explicitly allow it.

But a state management bug might let an attacker trick the operating system into thinking the user has granted permission – when in fact, they haven’t.

The app cannot access your location.

A vulnerable system might incorrectly remember (“state management”) that it had that approval and silently grant access.

Exploit Scenario (In Code)

Here’s a basic Swift code snippet showing how an attacker’s app might *test* whether it could get secrets before the patch:

import Contacts

let store = CNContactStore()

store.requestAccess(for: .contacts) { (granted, error) in
    if granted {
        // Normally allowed: Grab contacts
        let keys = [CNContactGivenNameKey, CNContactFamilyNameKey]
        let request = CNContactFetchRequest(keysToFetch: keys as [CNKeyDescriptor])
        do {
            try store.enumerateContacts(with: request) { (contact, stop) in
                print("\(contact.givenName) \(contact.familyName)")
            }
        } catch {
            print("Error fetching contacts")
        }
    } else {
        // Normally, here the app is denied
        print("Access not granted.")
    }
}
// On a vulnerable system, “granted” might be true because of a bug – even if the user denied access!

A malicious app might repeatedly check or trigger bugs in how the OS manages “Did the user say yes?” and “Has this app ever been granted access?” Once state gets out of sync, the system could eventually leak data.

Was It Used in the Wild?

No public exploits for CVE-2023-42839 have been documented as of June 2024. Apple’s security reports (HT213969, HT213837) do not mention confirmed attacks in the wild, but this is the kind of vulnerability that could go unnoticed if abused quietly by apps.

How Was It Fixed?

Apple says the problem was “addressed with improved state management.”

Whether those permissions are up-to-date and correctly enforced

After updates, the OS double-checks before letting any app into your sensitive data silos, making it far harder for mistakes or bugs to grant accidental access.

Make sure you’re running at least

- iOS/iPadOS 17.1

References

- Apple Security Updates (HT213969)
- Apple Security Updates (HT213837)
- MITRE CVE Details for CVE-2023-42839

Conclusion

CVE-2023-42839 is a classic example of how even industry giants make mistakes – and more importantly, how quickly they can fix them. Apple’s response was to improve how their systems track app permissions. As always, keeping your devices up to date is your best defense against security bugs, big or small.


If you found this helpful, consider sharing with fellow Apple users to keep everyone safe!

Timeline

Published on: 02/21/2024 07:15:48 UTC
Last modified on: 11/21/2024 15:15:13 UTC