Bluetooth is everywhere—from your headphones to your car’s entertainment. But a newly published vulnerability, CVE-2023-24023, proves that even the most common tech is never fully safe. In this post, we’ll break down what BLUFFS is, how it messes with your devices, and walk through real exploit details. No jargon—just essential info, code snippets, and original sources.

What is CVE-2023-24023? 📡

CVE-2023-24023, also known as BLUFFS, is a Bluetooth vulnerability discovered by Daniele Antonioli in 2023. It targets Bluetooth BR/EDR devices using Secure Simple Pairing (SSP) and Secure Connections (SC) from Bluetooth Core v4.2 up to v5.4. BLUFFS lets an attacker set a *short encryption key*, making your supposedly secure wireless connection much easier to break.

How BLUFFS Works: Key Points

BLUFFS (“Bluetooth Low-energy Unauthorized Framing and Fooling of Secure Simple”) exploits a weak link in how some Bluetooth devices negotiate encryption keys. Here’s how:

Bluetooth devices must agree on an encryption key length during pairing.

2. Spec flaw: The “master” device (the one initiating) can propose a super short key (as few as 1 byte!).
3. Victim device may accept this weak key, especially if it follows the flawed spec in Bluetooth v4.2-5.4.

With the key, the attacker can inject fake messages.

It’s a classic “man-in-the-middle” (MitM) attack, but possible even if you thought you had a secure pairing method.

Real World Attack Scenario 🛠️

Imagine Alice’s Bluetooth keyboard is paired to her PC. Bob, the attacker, sets up a rogue device close by and waits for Alice to reconnect.

Step by Step BLUFFS

- Step 1: Bob records the pairing traffic using a tool like _Ubertooth One_ (link).
- Step 2: Bob intercepts the key negotiation, injects a request for a “short key” (say, 8 bits).

Step 3: The keyboard accepts! All messages now use the weak key.

- Step 4: Bob brute-forces the key (256 tries for 8 bits, super fast) and listens to Alice’s keystrokes or sends fake ones (like “run virus.exe”).

Proof-of-Concept: Simple Code

Though real-world Bluetooth packet sniffing and injection is complex (see original researcher’s GitHub), here’s a simplified pseudocode to show how the brute-force works after capturing a weak LTK (Long Term Key):

# Assume you've sniffed ciphertext and the short 8-bit key is used.

ciphertext = b'\xab\xcd\x12'   # Example encrypted data
keyspace = 2**8  # Just 256 possible keys!

for key_candidate in range(keyspace):
    decrypted = my_decrypt(ciphertext, key_candidate)
    if is_valid_bluetooth_packet(decrypted):
        print(f"Key found: {key_candidate}")
        break

This brute-force is lightning fast—imagine how disastrous if your keyboard, headphones or car unlock responded to a hacked signal!

Is My Device Affected?

- If your device uses Bluetooth BR/EDR (not just BLE), was released after 2015, and is not running the latest firmware, it’s probably affected if:

The firmware allows short encryption keys.

- Your OS/Bluetooth stack hasn’t been patched after February 2023.

Patch. Patch. Patch!

- Update your device firmware and OS: Vendors are gradually releasing patches. Apple, Google, Microsoft, and Intel have all published updates.

Original References & Further Reading

- BLUFFS Announcement (by Daniele Antonioli)
- CVE-2023-24023 NIST Entry
- BLUFFS Research Paper (PDF)
- Technical Proof of Concept (PoC) on GitHub

Final Thoughts

CVE-2023-24023 (BLUFFS) isn’t just a bug—it’s a call to take Bluetooth security seriously. If your device maker hasn’t commented or released updates, contact them! Remember, the “Secure” in Secure Simple Pairing is only as strong as developers make it.

Timeline

Published on: 11/28/2023 07:15:41 UTC
Last modified on: 12/02/2023 04:40:02 UTC