An access control issue in the authentication module of Lexar_F35 v1.0.34 allows attackers to access sensitive data and cause a Denial of Service (DoS). An attacker without access to securely protected data on a secure USB flash drive can bypass user authentication without having any information related to the password of the registered user. The secure USB flash drive transmits the password entered by the user to the authentication module in the drive after the user registers a password and then the input password is compared with the registered password stored in the authentication module. Subsequently the module returns the comparison result for the authentication decision. Therefore an attacker can bypass password authentication by analyzing the functions that return the password verification or comparison results and manipulate the authentication result values. Accordingly even if attackers enter an incorrect password they can be authenticated as a legitimate user and can therefore exploit functions of the secure USB flash drive by manipulating the authentication result values.