John Brennan
took a polygraph test in 1980 as part of the initial application process to join the CIA as a career employee, not specifically before his Senate confirmation as Director. All permanent CIA employees are required to undergo polygraph interviews as part of their comprehensive security and background checks.
During that initial polygraph, Brennan disclosed that he had voted for the Communist Party candidate in the 1976 presidential election as a form of protest. He initially feared this admission would disqualify him, but he was hired anyway, a story he has shared publicly to illustrate the agency's value for candor and free expression.
The confirmation process for the Director of the CIA, which involves a Senate vote, requires a thorough background investigation and a security clearance, but a separate, specific polygraph test is not a mandatory part of the Senate confirmation itself. The polygraph is a standard requirement for initial CIA employment and maintaining the necessary high-level security clearance throughout one's career at the agency.