A flaw in a Bluetooth protocol is leaving millions of devices vulnerable to attacks, according to a study released by a Swiss research institute.

The vulnerability, called Bluetooth Impersonation AttackS (BIAS), allows an intrusion by an attacker posing as a previously trusted Bluetooth device.

“In this paper, we demonstrate that the Bluetooth standard contains vulnerabilities enabling an attacker to impersonate a device and to establish a secure connection with a victim, without possessing the long term key shared by the impersonated device and the victim,” researchers at the Swiss Federal Institute of Technology Lausanne said in their report.