CVE-2025-24203 - How a macOS/iPadOS App Could Break Into Protected System Files (And How Apple Fixed It)

In early 2025, security researchers discovered a serious bug in Apple’s macOS and iPadOS systems. Tracked as CVE-2025-24203, this vulnerability let malicious apps edit protected parts of the file system—something that shouldn’t be possible unless you have root access or special system permissions. Apple has since squashed the bug with updates, but it’s a fascinating example of how small oversights in permission checks can put users at risk.

Let's break down what happened, how the issue worked, see a code snippet showing the risk, and show how Apple fixed things. This post is exclusive and written in plain English for everyone.

What Was the Problem?

On devices running vulnerable versions of macOS and iPadOS, certain apps could bypass system-level file protections. This meant a poorly behaving app could change, delete, or corrupt files that are key to your system’s stability or security. Normally, System Integrity Protection (SIP) and sandboxing features make sure this can’t happen, but due to weak validation in file access routines, attackers found a loophole.

A Peek at the Vulnerable Code

*Note: This code is a simplified illustration; the real exploit was more complex and involved Apple’s proprietary frameworks.*

Imagine the system function that checks if a file can be modified looks like this

BOOL canModifyFile(NSString *filePath) {
    // Insecure check (before the fix)
    if (![filePath hasPrefix:@"/System/"]) {
        return YES;
    }
    return NO;
}

A sneaky attacker could use a trick called "path traversal" or symbolic links (“symlinks”) to trick the check, such as:

ln -s /System/Library/ImportantFile /tmp/fakefile
myMaliciousApp edit /tmp/fakefile

The system thought /tmp/fakefile was safe, but it actually altered a file inside /System/Library/.

How Could Attackers Exploit This?

Attackers would craft an app that secretly created symlinks or used tricky Unicode path names to fool the file system’s protective checks. Once in, their app could:

Subvert privacy settings, like disabling security features

All this could happen without triggering SIP’s usual alarms! That’s pretty scary.

macOS Sequoia 15.4

They improved the file modification checks to resolve any symlink or path traversal tricks before allowing writes. After the fix, the code acts more like:

BOOL canModifyFile(NSString *filePath) {
    // Stronger check after fix: resolves real file location
    NSString *realPath = [[NSFileManager defaultManager] destinationOfSymbolicLinkAtPath:filePath error:nil];
    if ([realPath hasPrefix:@"/System/"]) {
        return NO;
    }
    // ...additional checks...
    return YES;
}

With these added validations, apps can’t disguise their target files, and the system protection is restored.

Check official sources:

- Apple’s Security Updates for macOS
- Apple’s Security Updates for iOS/iPadOS
- Official CVE Record for CVE-2025-24203 (when available)

Summary

CVE-2025-24203 was a dangerous flaw that let bad apps tamper with the core system files on macOS and iPadOS. By improving checks and closing loopholes, Apple quickly made things safe again. The lesson here: no matter how strong your protections, attackers will look for the tiniest cracks—so always keep your devices up to date.

Timeline

Published on: 03/31/2025 23:15:18 UTC
Last modified on: 04/07/2025 13:43:03 UTC