Today’s vehicles run three incompatible Layer-2 security stacks: MACsec on Ethernet, SecOC on CAN FD, and CAN XL currently specifies CANsec. We show how to collapse all three into one – by reusing MACsec as the security engine for CANsec on CAN XL (CiA 613-2), and extending it to CAN FD via the CAN FD Adaptation Layer (FDAL). The result is a consistent foundational security layer for the whole in-vehicle network, from Ethernet to CAN XL and CAN FD.