A Hardware Security Module (HSM) is one of the most secure devices designed to store cryptographic keys securely and prevent attacks ranging from remote to physical access. This talk will offer an in-depth exploration of HSM security and present a vulnerability discovered in PowHSM, an open-source HSM solution built on the Ledger Nano S device. The presentation will detail the process of identifying the vulnerability in the USB stack and demonstrate a proof-of-concept (PoC) for recovering private keys from the device.