On BC Vault devices, a side channel for the row-based SSD1309 OLED display was found.

Summary

On BC Vault devices, a side channel for the row-based SSD1309 OLED display was found. The power consumption of each row-based display cycle depends on the number of illuminated pixels, allowing a partial recovery of display contents. For example, a hardware implant in the USB cable might be able to leverage this behavior to recover a data value. In other words, the side channel is relevant only if the attacker has enough control over the device's USB connection to make power-consumption measurements at a time when secret data is displayed. The side channel is not relevant in other circumstances, such as a stolen device that is not currently displaying secret data. NOTE: the vendor's position is that there is no security impact: the only potentially leaked information is the number of characters in the PIN