Remove mold with equal parts water and vinegar, mix in a spray bottle, spray. Now then there’s a different type of molding on the edge of box springs. Which are you referring to?
I'd do what Dfm suggested and then if you can, let it dry in direct sun for an afternoon
I, myself would use full strength vinegar for maximum spore killing. Make sure you get it into the fabric deep enough to get to all the mold/mildew. The vinegar should also take care of the moldy smell, if it didn't, all areas weren't covered and their is some still growing somewhere. Once the vinegar dries, give it a sniff test to make sure you don't need to apply in other areas.
Hi RJW: If it's in just certain areas, you can mix equal amounts of rubbing alcohol (isopropyl alcohol) and warm water in a disposable container. Dip a cloth into it, wring it out, and use this wet cloth to scrub the mouldy area of the mattress. Use a circular motion when scrubbing, and go well beyond the area of visible mould. Lysol can be a good choice for blasting mold out of a mattress, though you can certainly also employ rubbing alcohol, bleach, or white vinegar. To use one of those options, apply to a sponge or rag and scrub at the moldy spots until they're gone. Then, if you can put it out in the sun, that would be good. If not, then put a fan on it so that it will dry out quickly. Good luck