never heard of a "finish" that smelled of decay. I've worked in cabinet shops, building wooden fixtures and furniture.
What brand is this? The manufacturere might be able to help.
Also, is there a case? Cases can collect mildew, as well as leather straps. Some leather straps actually start our smelling rotten (china) cuz they are cured in cow urine, believe it or not (as told to me by the owner of Bates Leather Manufacturing). That's why it smells bad in some spots at flea markets or street sales.
For the actual guitar wood to have an odor at all would mean that the stench has permeated the finish (nearly impossible, since most neck-throughs have a finish approaching or equal to automotive-grade) or it is "in " the guitar. Remove the pick-guards, pick-up covers, truss-rod covers, and routing /battery covers on the front and back of the guitar. See if the smell is stronger there.
Then proceed with an air nozzle if you have a compressor. If not, go to the gas station/garage. Blow into these holes several times, careful not to lose any hardwar (washers, etc).
you can then put a powder disinfectant into the holes, and leave it there for a few days. Then blow it out or vacuume it out. Do this several times til the smell is tolerable.