Munster held on to top spot in the Pro12 going into the autumn internationals but may yet regret letting Ospreys escape with a late bonus point.
Ospreys out-half Matthew Morgan was off-target with a drop-goal two minutes from time but Ronan O'Mahony was adjudged to have taken the ball back over the endline.
Ospreys won the scrum and forced a penalty and Morgan grabbed the bonus point with the last kick of a disappointing match.
Neither side managed to get across the gain-line with any degree of consistency in the opening half and Munster went in leading by 6-3 at the break.
They thought they had crossed for the opening try just before the interval when Ivan Dineen touched down after being put through by the hands of Duncan Williams and Ian Keatley.
But referee Giuseppe Vivarini went to the TMO and – as Keatley lined up the conversion – TMO Jude Quinn judged that a scrum on an Ospreys put-in was incomplete when Munster turned it over, and ruled out the try.
It was as near as either side came to getting a try in a dull opening half which bore little resemblance to a clash between two sides level on points at the top of the table. Both may have been without most of their internationals but it was a first period where neither defence had to stretch to keep their line intact.
Munster hit the front after five minutes when a penalty won at a scrum resulted in Keatley making no mistake from the 22. He was off-target nine minutes later with a difficult effort from the left as Munster tried to turn early dominance into scores. But Ospreys defended well and chances were scarce, although Keatley made it 6-0 after 21 minutes after Ospreys hooker Scott Baldwin was penalised for being offside.
Ospreys finally got moving and worked the ball through the hands in a couple of promising attacks and got off the mark with a penalty in front of the posts from Morgan after 25 minutes.
The Welsh rarely threatened from then until the break and they were relieved when the TMO's decision meant they were just three rather than 10 adrift at the interval.
However, the next intervention from the TMO went against them, with Tito Tebaldi adjudged not to have released when he was driven over the line six minutes after the restart.
Keatley was off-target with a 43-metre penalty five minutes later but then extended Munster's lead when he landed his third kick of the night with a penalty on the 10-metre line.
The game became even more disrupted as both sides began to empty their benches and rain began to fall, but Munster looked like they would force Ospreys to leave pointless when young outhalf JJ Hanrahan landed his only kick of the night with a penalty from 25 metres on the right, 12 minutes from the end.
Morgan was badly wide with a penalty from the left 10 minutes from time and then saw a late drop-goal skew away from the posts but when O'Mahony was penalised for bringing the ball over the line, Morgan kept his nerve to salvage the bonus point.
Scorers – Munster: Keatley 3 pens, Hanrahan pen. Ospreys: Morgan 2 pens.
Munster: F Jones; J Murphy, C Laulala, I Dineen, R O'Mahony; I Keatley (JJ Hanrahan 64), D Williams (C Sheridan 56); D Kilcoyne (J Cronin 71), D Varley, BJ Botha (J Ryan 40); Donncha O'Callaghan, D Foley; Dave O'Callaghan (B Holland 71), S Dougall (J Coughlan 60), CJ Stander.
Ospreys: R Fussell (S Davies 64); A Natoga (H Dirksen 50), J Spratt, A Bishop, B John; M Morgan, T Tibaldi (T Habberfield 71); M Thomas (N Smith 67), S Baldwin, J Rees (D Suter 71); L Peers, J King (R Hughes 68); J Bearman, S Lewis, M Allen.
Referee: G Vivarini (FIR).