The Motorola MDLC protocol through 2022-05-02 mishandles message integrity. It supports three security modes: Plain, Legacy Encryption, and New Encryption. In Legacy Encryption mode, traffic is encrypted via the Tiny Encryption Algorithm (TEA) block-cipher in ECB mode. This mode of operation does not offer message integrity and offers reduced confidentiality above the block level, as demonstrated by an ECB Penguin attack against any block ciphers.