The Cable Assistive Rehabilitation Elbow Exoskeleton is an active arm assistance device for in-home rehabilitation for individuals who suffered a traumatic brain injury, such as stroke, that experienced elbow flexion/extension impairment. A robotic elbow exoskeleton can provide ongoing therapeutic treatment to retrain arm movement functionality to perform activities of daily living. Providing an accessible, lightweight robotic exoskeleton is an ongoing challenge for wearable devices. Our proposed elbow exoskeleton introduces a cable-driven design using a bidirectional, dual pulley system mated with a high torque motor and a custom 17.5:1 planetary gearbox manufactured using high strength engineering stereolithography resin material. The cable-driven dual pulley system transfers the rotary motion to actuate an arm brace for elbow joint flexion and extension. Benchtop experiments demonstrated a maximum output torque of 26 Nm while lifting a 1 kg object. Results exceeded the minimum joint torque and velocity requirement to carry out day-to-day lifting activities. The designed actuation system provided a transmission mass reduction of 39% compared to conventional actuators, lowered overall cost by applying rapid fabrication techniques, and provided formability for a compact elbow exoskeleton design. In all, the system weighs less than 8.5 kg that can translate the unit to an in-home rehabilitation device.