Do a Google search on wood restoration. Saw a company online recently that offered different viscosities of cyanoacrylate resins for wood repair. Sometimes these are used to firm up old soft wood prior to an epoxy repair. If the area isn't all that big, just buy some Crazy Glue, the usual consumer form of cyanoacrylate resin we are all familiar with. Then cover the bad spots with it, put down a sheet of polyethylene film on top, something flat and heavy on top of that and let it cure. Light sanding and recoating with a water based poly varnish ouhgt to do it. HTH
Joe