how to access grub menu when it is locked with a password

I am running a CentOS-7 virtual machine and I have the task of recovering the root password of the system. But the GRUB menu is locked with Password-Based Key Derivation Function 2. Therefore I cannot just press 'e' at the grub menu. Can anyone help point me in the right direction? I have no clue where to start. Google searches only bring up people talking about pressing 'e' at the GRUB menu which isn't possible here.