Systems and methods for protocol-tolerant communications in a Controller Area Network (CAN) are described. In some embodiments, a method may include receiving a frame at a network node; identifying, by the network node, a bit in a selected field of the frame; and determining, by the network node, that the frame follows a second format despite the bit indicating that the frame follows a first format. In other embodiments, a CAN controller includes message processing circuitry; and a memory coupled to the message processing circuitry, the memory having program instructions that configure the message processing circuit to: receive a frame; identify a bit in a selected field of the frame; and determine that the frame follows a Classical CAN format despite the bit indicating that the frame follows a flexible data-rate CAN (CAN FD) format.