The connection_edge_process_relay_cell_not_open function in src/or/relay.c in Tor 0.2.x before 0.2.0.35 and 0.1.x before 0.1.2.8-beta allows exit relays to have an unspecified impact by causing controllers to accept DNS responses that redirect to an internal IP address via unknown vectors.  NOTE: some of these details are obtained from third party information.