It might have been three, had Jamie Roberts not flung a forward pass to Owen Williams in the 68th minute when the right wing - scorer of his side's opening try - had the line at his mercy.
The sides were tied 3 points apiece at the break after a pretty turgid opening in which Munster created plenty but spoiled their work with a succession of errors.
A further error on half way at the start of the second half ended with Williams romping home for the opening try and though Ronan O'Gara reduced the deficit to four points with a penalty moments later, it was the visitors who enjoyed the better of the exchanges with Robin Copeland sealing the outcome with a try in the 69th minute.
Munster: F Jones; D Howlett, K Earls, J Downey, D Hurley; R O'Gara, C Murray; D Kilcoyne, M Sherry, S Archer; D Foley, D Ryan; T O'Donnell, S Dougall, J Coughlan. Replacements: S Henry, W du Preez, BJ Botha, B Holland, CJ Stander, D Williams, I Keatley, C Laulala.
Cardiff Blues: J Tovey; O Williams, R Smith, J Roberts, H Robinson; R Patchell, L Jones; S Hobbs, R Williams, B Bourrust: B Davies, L Reed; J Navidi, S Warburton, R Copeland. Replacements: K Dacey, P Tamba, S Andrews, J Down, L Hamilton, A Walker, C Sweeney, L Halfpenny.
Referee: Nigel Owens