Conn. Gen. Stat. § 31-293a

If an employee or, in case of his death, his dependent has a right to benefits or compensation under this chapter on account of injury or death from injury caused by the negligence or wrong of a fellow employee, such right shall be the exclusive remedy of such injured employee or dependent and no action may be brought against such fellow employee unless such wrong was wilful or malicious or the action is based on the fellow employee's negligence in the operation of a motor vehicle as defined in section 14-1 . For purposes of this section, contractors' mobile equipment such as bulldozers, powershovels, rollers, graders or scrapers, farm machinery, cranes, diggers, forklifts, pumps, generators, air compressors, drills or other similar equipment designed for use principally off public roads are not “motor vehicles” if the claimed injury involving such equipment occurred at the worksite on or after October 1, 1983. No insurance policy or contract shall be accepted as proof of financial responsibility of the owner and as evidence of the insuring of such person for injury to or death of persons and damage to property by the Commissioner of Motor Vehicles required by chapter 246 if it excludes from coverage under such policy or contract any agent, representative or employee of such owner from such policy or contract. Any provision of such an insurance policy or contract effected after July 1, 1969, which excludes from coverage thereunder any agent, representative or employee of the owner of a motor vehicle involved in an accident with a fellow employee shall be null and void.