Insufficient length checks in the ShapeShift KeepKey hardware wallet firmware before 7.7.0 allow a global buffer overflow via crafted messages. Flaws in cf_confirmExecTx() in ethereum_contracts.c can be used to reveal arbitrary microcontroller memory on the device screen or crash the device. With physical access to a PIN-unlocked device, attackers can extract the BIP39 mnemonic secret from the hardware wallet.