Munster would make amends a few minutes later when he defused another bomb as Mamo was racing through on what would be the Knights' last roll of the dice.
The Storm momentarily move to the top of the NRL ladder with the victory, their 10th win in 11 games.
It was the Knights' 11th straight loss and they now appear destined for a second consecutive wooden spoon.
Newcastle dominated territory and enjoyed a 70 per cent share of possession in the opening 20 minutes, but couldn't manage to crack the Storm line.
Koroibete turned defence into attack in the 11th minute when he latched onto a spilled ball from Mamo and raced 85 metres to score.
Newcastle finally turned possession into points 10 minutes later when Mamo, who was filling in at fullback for Dane Gagai, took a short ball from halfback Trent Hodkinson and touched down to score.
The video ref had a look at a possible obstruction, but ultimately gave the Knights the green light, much to the chagrin of Storm skipper Cameron Smith.
But the Knights' lead was short-lived.
Only three minutes later Vunivalu latched onto a Munster cut-out pass, beating two defenders to touch down for his 17th try this season.
After halftime, Koroibete scored his second when he steamrolled over Knights winger Brendan Elliott to score in the corner.
The teams then traded tries before Mamo sailed past Munster to score and set the game up for an exciting finish.
- AAP