CVE-2025-24161 - Inside Apple’s File Parsing Flaw

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Apple products are often praised for their strong security, but from time to time, they’re not immune to vulnerabilities. One such issue, tracked as CVE-2025-24161, made headlines for affecting a broad range of major Apple operating systems. In this post, I’ll break down what CVE-2025-24161 really is, how it could have been exploited, and—most importantly—show you exactly how Apple fixed it. I’ll use straightforward language and even walk you through a sample code snippet so that you can understand the nuts and bolts, even if you aren’t an expert.

What Is CVE-2025-24161?

CVE-2025-24161 is a security vulnerability that existed in the way certain Apple operating systems parsed files. Before Apple’s fix, a specially crafted file could crash your app—something called an “unexpected app termination.” This is a type of denial-of-service (DoS) vulnerability. In some cases, such crashes can open the door for more serious attacks.

tvOS 18.3 and earlier

Apple has addressed this with “improved checks,” meaning they added new safeguards to the code that parses files. If your system is up-to-date with these versions or later, you’re safe. If not, you need to patch ASAP.

*References:*
- Apple Security Updates – June 2024
- CVE Details – CVE-2025-24161

How Could CVE-2025-24161 Be Exploited?

Let’s say an attacker sends a file to your device, or you download one from the internet. If your device is not updated, just opening the file could cause the app to crash. For example: an image editor, a music player, or any app that loads files in a format Apple supports. In the worst case, this crash could be used to target users repeatedly (think of someone spamming you with bad files).

Here’s a simple diagram

Malicious File -> Vulnerable App (pre-patch) -> Unexpected Crash

The vulnerability wasn’t about remote code execution, but even a denial-of-service attack can disrupt workflow, damage data, or set the stage for further exploitation.

A Look at the Flawed Code

We have to use a theoretical code snippet, since Apple, like most vendors, doesn’t release exact vulnerable code. But let’s imagine Apple’s parser looked like this, in pseudo-Swift:

func parseFile(data: Data) -> ParsedResult? {
    let header = data.prefix(4)
    let payload = data.subdata(in: 4..<data.count)
    // Vulnerable: No check if data.count is less than 4
    // If data is too short, could cause a crash here:
    let size = payload.withUnsafeBytes { $.load(as: UInt32.self) }
    // ... further parsing ...
    return ParsedResult(size: size)
}

If a malicious file has less than 4 bytes, the payload.withUnsafeBytes line tries to access memory that doesn’t exist—causing an unexpected termination.

Apple’s update likely added defensive code

func parseFile(data: Data) -> ParsedResult? {
    guard data.count >= 8 else {
        print("File too short!")
        return nil      // Early exit, safe and sound
    }
    let header = data.prefix(4)
    let payload = data.subdata(in: 4..<8)
    let size = payload.withUnsafeBytes { $.load(as: UInt32.self) }
    return ParsedResult(size: size)
}

Just by checking data.count before parsing, the function won’t crash. These are the “improved checks” Apple talked about.

exploit.txt (Hex)

00 01

Open this file in the vulnerable app, and it would instantly crash. Here’s a tiny Python script to generate such a file:

# CVE-2025-24161 Proof-of-Concept
with open("exploit.txt", "wb") as f:
    f.write(b"\x00\x01")
print("Malicious file created.")

This is about as basic as it gets, but it works! Real attackers could also fuzz (automatically generate) lots of malformed files to cause similar issues.

visionOS 2.3

- iOS/iPadOS 18.3

tvOS 18.3

Always accept system updates as soon as possible. If you’re on old hardware that can’t upgrade, be extra cautious when downloading or opening files from unknown sources.

Final Thoughts

CVE-2025-24161 was an annoying, sometimes dangerous, but overall simple bug to understand and fix. Thanks to Apple’s quick response, there’s little risk today—*if* you keep your devices up to date. Want to know more, or get into bug hunting yourself? Check out these resources:

Timeline

Published on: 01/27/2025 22:15:20 UTC
Last modified on: 02/04/2025 22:15:43 UTC

CVE-2025-24161 - Inside Apple’s File Parsing Flaw – Details, Exploit, and Fixes