A flawed protocol design in the Ledger Monero app before 1.5.1 for Ledger Nano and Ledger S devices allows a local attacker to extract the master spending key by sending crafted messages to this app selected on a PIN-entered Ledger connected to a host PC.
ledger
CVE-2019-14354
On Ledger Nano S and Nano X devices, a side channel for the row-based 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 confidential secrets such as the PIN and BIP39 mnemonic. 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.