Challenger 300 pilot reported being notified by the Cabin Host of moderate-heavy smoke emanating from the forward closet. Flight crew completed a safe overweight landing followed by everyone safely vacating aircraft safely.

Narrative

Enroute ZZZ-ZZZ1; FL390. Cabin Host (CH) alerted crew to smoke in galley. I went to galley and there was mod to heavy smoke coming out of closet forward of galley. Appeared to be coming from behind panels. I could not identify source. I turned off AC & DC power to cabin / galley. I [requested priority] handling and ATC gave options to divert to ZZZ2 or ZZZ3. ZZZ3 was closer and weather was good. We initiated a descent and proceeded to ZZZ3. CH kept me informed on the smoke. Was isolated to the galley area and was not entering the cabin. I elected not to drop the O2 masks. I had the CH take a seat in the cabin. I elected to land 1000 lbs over weight. We landed Runway XX; exited to the right on Taxiway 1 and shut plane down and had everyone vacate plane. By that point the smoke had dissipated but was still very strong odor of burned electrical. With all power off plane and batteries disconnected no evidence of continuing smoke or issues. After about 30 minutes; FBO towed the plane to the FBO. Was determined to be failed Data Concentrator Unit (DCU) and DCU Fan. Equipment failure. Nothing would prevent from happening again that I'm aware of.