The airbag detonation algorithm allows injury to passenger-car occupants via predictable Security Access (SA) data to the internal CAN bus (or the OBD connector). This affects the airbag control units (aka pyrotechnical control units or PCUs) of unspecified passenger vehicles manufactured in 2014 or later, when the ignition is on and the speed is less than 6 km/h. Specifically, there are only 256 possible key pairs, and authentication attempts have no rate limit. In addition, at least one manufacturers interpretation of the ISO 26021 standard is that it must be possible to calculate the key directly (i.e., the other 255 key pairs must not be used). Exploitation would typically involve an attacker who has already gained access to the CAN bus, and sends a crafted Unified Diagnostic Service (UDS) message to detonate the pyrotechnical charges, resulting in the same passenger-injury risks as in any airbag deployment.
The product uses a broken or risky cryptographic algorithm or protocol.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Pcu | Pcu | 2014 (including) | 2014 (including) |
Cryptographic algorithms are the methods by which data is scrambled to prevent observation or influence by unauthorized actors. Insecure cryptography can be exploited to expose sensitive information, modify data in unexpected ways, spoof identities of other users or devices, or other impacts. It is very difficult to produce a secure algorithm, and even high-profile algorithms by accomplished cryptographic experts have been broken. Well-known techniques exist to break or weaken various kinds of cryptography. Accordingly, there are a small number of well-understood and heavily studied algorithms that should be used by most products. Using a non-standard or known-insecure algorithm is dangerous because a determined adversary may be able to break the algorithm and compromise whatever data has been protected. Since the state of cryptography advances so rapidly, it is common for an algorithm to be considered “unsafe” even if it was once thought to be strong. This can happen when new attacks are discovered, or if computing power increases so much that the cryptographic algorithm no longer provides the amount of protection that was originally thought. For a number of reasons, this weakness is even more challenging to manage with hardware deployment of cryptographic algorithms as opposed to software implementation. First, if a flaw is discovered with hardware-implemented cryptography, the flaw cannot be fixed in most cases without a recall of the product, because hardware is not easily replaceable like software. Second, because the hardware product is expected to work for years, the adversary’s computing power will only increase over time.