In July 2023, Apple released macOS Ventura 13.5 addressing several security issues. One of them, CVE-2023-38609, could let a malicious app bypass “Privacy” settings and gain access to sensitive resources – *even if* you thought you’d locked them away. This issue was due to an injection bug and improper input validation inside the TCC (Transparency, Consent, and Control) subsystem that controls app permissions in macOS.

Let’s break down what happened, how it worked, show some example exploit code, and talk about how to stay safe.

What is CVE-2023-38609?

According to Apple’s advisory, this bug allowed a local app to bypass some Privacy preferences. For instance, an app not given permission to access your contacts or microphone *could* trick macOS into letting it in.

The root cause was an *injection issue* — the system didn’t properly validate data received from apps, meaning a clever attacker could smuggle in malicious input and confuse the operating system’s privacy checker.

A Closer Look: How did the Vulnerability Work?

macOS uses a privacy system called TCC. When an app wants to access hardware (Like your camera or microphone) or personal data (like contacts, photos, calendar events), TCC asks you for permission and saves your choices.

But under the hood, TCC relies on certain system APIs where apps send data — like the bundle identifier and code signature — to request access.

The bug: Apps could tamper with the input passed to these APIs, *injecting* falsified or malformed values. With the right tricks, you could tell TCC "I’m a trusted system app, let me in!" and bypass certain permission checks.

Exploit Example (Proof of Concept)

Here’s a simplified code example in Objective-C showing how one could try to request contact access with a spoofed bundle ID on vulnerable systems:

// WARNING: For educational purposes only. Do not use on others' devices.

#import <Foundation/Foundation.h>
#import <Contacts/Contacts.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        CNContactStore *store = [[CNContactStore alloc] init];

        // Normally, the system checks the bundle identifier here.
        // Vulnerable systems did not check properly, so an attacker
        // could inject/swap this value (in low-level syscalls or via DYLD).
        //
        // Simulated here:
        [[NSUserDefaults standardUserDefaults] setObject:@"com.apple.Mail" forKey:@"CFBundleIdentifier"];

        [store requestAccessForEntityType:CNEntityTypeContacts completionHandler:^(BOOL granted, NSError * _Nullable error) {
            if (granted) {
                NSLog(@"[+] Got access to contacts!");
            } else {
                NSLog(@"[-] Access denied.");
            }
        }];

        [[NSRunLoop currentRunLoop] run];
    }
    return ;
}

Note: The real-world exploit used much more sophisticated injection, tampering with XPC (Cross Process Communication) pipes or dynamic libraries to make the system service believe it was being contacted by a trusted app.

Technical write-ups (for advanced users)

- macOS Privacy Bypass Internals (by Theori)
- Apple’s Security Release Note

How Was It Fixed?

Apple’s patch for CVE-2023-38609 improved input validation. Now, when apps request sensitive permissions, the TCC subsystem crosschecks input data more thoroughly. Malicious apps can’t lie about their identities or inject bad info, so the privacy wall holds firm.

Update your Mac: Make sure you’re running at least macOS Ventura 13.5 or later.

2. Be cautious: Only install software from developers you trust. Malicious software often tries to exploit these vulnerabilities before they’re patched.
3. Review Permissions: Open System Settings → Privacy & Security, and double-check which apps have access to your data.

Conclusion

CVE-2023-38609 reminds us that even modern operating systems can have subtle (but serious) privacy lapses. With improved input validation, Apple closed this loophole, but attackers are constantly looking for new ones. Stay vigilant and always keep your software updated!

References

- Apple Security Updates for macOS Ventura 13.5 (HT213841)
- Apple’s CVE page
- Theori: Inside macOS Privacy Bypass Bugs


*Stay safe, update often, and keep an eye on your privacy settings!*

Timeline

Published on: 07/28/2023 05:15:11 UTC
Last modified on: 08/03/2023 18:09:27 UTC