Researchers discover a severe security hole in Bluetooth devices

27 Jul 2018

Image: successo images/Shutterstock

A validation flaw in Bluetooth communication opens the door for attackers.

Bluetooth is one of the most common technological protocols we use today. However, a cryptographic bug in many Bluetooth OS and firmware drivers could permit an attacker within approximately 30 metres to obtain and decrypt information shared between Bluetooth-paired devices.

Prof Eli Biham and Lior Neumann of the Israel Institute of Technology located the flaw (CVE-2018-5383), which has been flagged by CERT of Carnegie Mellon University. It has been confirmed to affect Apple, Intel, Broadcom and Qualcomm hardware as well as some Android handsets. It affects both Secure Simple Pairing and Low-Energy (LE) Secure Connections for Bluetooth.

Cryptographic flaw

The flaw is due to some vendors’ implementations of Bluetooth improperly validating the cryptographic key exchange that occurs when Bluetooth devices are pairing. The weakness is within the key exchange implementation, which uses a mathematical concept dubbed elliptic-curve cryptography. The particular version affected is the elliptic-curve Diffie-Hellman key exchange, used to establish a secure connection over an insecure channel.

This problem could allow a nearby attacker within radio range to remotely inject a bogus public key during the public-private key exchange. This could pave the way for a man-in-the-middle attack whereby someone could “passively intercept and decrypt all device messages, and/or forge and inject malicious messages”.

Potential for eavesdropping

Biham explained further: “The technology we developed reveals the encryption key shared by the devices, and allows us or a third device to join the conversation. We can eavesdrop on or sabotage a conversation. As long as we do not actively participate, the user has no way of knowing that there is a third party listening in.”

The Bluetooth Special Interest Group, which oversees communication protocol standards, stated: “The researchers identified that the Bluetooth specification recommends, but does not require, that a device supporting the Secure Simple Pairing or LE Secure Connections features validate the public key received over the air when pairing with a new device.

“It is possible that some vendors may have developed Bluetooth products that support those features but do not perform public key validation during the pairing procedure. In such cases, connections between those devices could be vulnerable to a man-in-the-middle attack that would allow for the monitoring or manipulation of traffic.”

Manufacturers were warned of the flaw in January, so have had a number of months to develop solutions and patches. Fixes in both software and firmware are required to protect devices against the flaw. Apple has already released a patch, as well as Google, Dell, Qualcomm, Broadcom and Lenovo.

Ellen Tannam was a journalist with Silicon Republic, covering all manner of business and tech subjects