When it comes to modern cars, the infotainment system (the screen and controls for audio, navigation, and other features) is almost as important as the engine. But as these systems become more complex, they're also more exposed to bugs and vulnerabilities. Today, we're digging deep into one such bug: CVE-2023-34406, a recent vulnerability found in the Mercedes Benz NTG 6 (New Telematics Generation 6) head units that could allow someone to repeatedly crash the User-Data service. Let's break down what this means, how it works, and what the implications are for regular drivers.

What Is CVE-2023-34406?

On Mercedes Benz cars equipped with the NTG 6 infotainment (or "head unit"), there's a feature that lets you import or export user data — things like settings, playlists, or contacts — using a USB stick. Researchers found that if someone plugs in a USB with carefully crafted data, they can trigger an integer overflow in the software that processes these files. In turn, this can crash the User-Data service responsible for handling such imports/exports.

The service doesn't stay offline forever; it restarts itself. But with repeated attacks, a determined hacker can make it keep crashing, causing headaches for the driver.

Understanding the Issue: What’s an Integer Overflow?

In simple terms, computers store numbers in a specific way (for example, a 32-bit number goes from to 4,294,967,295). Integer overflow happens when software tries to process a number bigger than its storage can handle — it "wraps around" to zero or a small number. This confuses software, sometimes causing crashes or unpredictable behavior.

Here's a mini code snippet showing how this bug typically happens

// Hypothetical code in import function
uint32_t data_size = read_data_size_from_usb();
// Attacker supplies data_size = xFFFFFFFF

char *buffer = malloc(data_size);
if (buffer == NULL) {
    // allocation failed, handle error
}
read_data(buffer, data_size);

If data_size is super-large (like xFFFFFFFF, the max for an unsigned 32-bit int), the malloc might fail, or memory gets misused, leading to a crash.

Exploiting the NTG 6: Step by Step

Important: This vulnerability requires physical access — an attacker must plug a USB into the car. No remote attacks.

Prepare a Malicious USB Stick:

Create an export file (it could be as simple as a settings file) that, when loaded, contains manipulated data fields (such as a size value set to the maximum 32-bit integer).

Import the File:

Start the import process from the infotainment menu. The system will process the file and hit the integer overflow.

Watch the Crash:

The User-Data service fails (possibly with an error pop-up or simply returning to the main menu). It will then restart, but you could repeat the process to keep it down.

Real-World Impact

- No car control or remote takeover. This bug only crashes the User-Data service on the display.

No data theft. It's a denial-of-service (DoS) bug.

- Annoyance factor. The driver might be unable to import/export data, or the infotainment system could act flaky if attacked repeatedly.

Here’s a basic gist of how an attacker might construct an "evil" settings file (pseudocode)

with open('malicious_settings.bin', 'wb') as f:
    # Write a fake header
    f.write(b'\xDE\xAD\xBE\xEF')
    # Write an 'exported data size' as the max unsigned int
    f.write((xFFFFFFFF).to_bytes(4, 'little'))
    # The rest of the data can be random or empty

The actual file format may be more complex, but this shows the idea.

Don't insert random USB sticks: Only use your own media.

- Keep your car software updated: Car makers regularly push patches; check with your dealer for updates.
- Be careful sharing export/import files: Only transfer user settings or data between your own devices.

Mitigation and Official Response

Mercedes Benz is aware of this issue and has assigned the identifier CVE-2023-34406. Patches may already be available for affected vehicles. Contact your Mercedes dealer or visit their security advisory page for updates.

Official advisory:
- Mercedes Benz Cybersecurity Advisories
- CVE-2023-34406 entry at NVD

Conclusion

CVE-2023-34406 sounds scarier than it is for most people. Still, it’s a reminder that even “small” car functions can have bugs. For hackers, it’s only a stepping stone — but for car lovers, it’s a good reason to keep your software fresh and don’t plug in untrusted devices.

References

- Mercedes Benz IT Security
- NIST NVD: CVE-2023-34406
- What Is Integer Overflow? (OWASP)_


*This article is written exclusively for you by our team – feel free to share it with friends concerned about car cybersecurity!*

Timeline

Published on: 02/13/2025 23:15:09 UTC
Last modified on: 03/17/2025 19:15:20 UTC