The five cases happened between 1 July 2014 and 30 June 2015, the report said.
The UN report does not include information on any criminal charges brought against the former staff.
The four staff sacked for possession of child pornography were dismissed under "misuse of United Nations information and communications technology", the report said.
The report details disciplinary actions for misconduct and criminal behaviour involving the UN secretariat`s 41,000 staff. It does not specify where the former staff were stationed, or when they were dismissed.
One staff member took cash from the luggage of a passenger on a UN flight
Any cases involving criminal conduct were referred to authorities in the staff member`s country, a spokesman for the UN, Farhan Haq, said on Friday.
"While the United Nations can and does follow up with member states, the national authorities concerned have the sole prerogative in determining what, if any, investigations or proceedings are initiated against the individuals," he said.
He said those authorities would decide whether to provide any further information to the UN.
The report also listed other cases of misconduct and the actions taken. A staff member who stored pornography involving adults was disciplined with demotion and a ban on promotion for two years.
Another, responsible for security screening at an airport, had their employment terminated after taking $2,200 (£1,440) from the luggage of a passenger on a UN flight.
The report details a number of dismissals relating to a staff protest at a peacekeeping mission, in which one UN staff member "disarmed a military officer".
Others at the same protest "improperly restricted" movement of people and vehicles, "intimidated and/or physically assaulted" people, damaged a UN vehicle, and allowed journalists on-site without authorisation, the report said.
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