Re: is this fixable?
Well, it's sure not safe like that. Depending on the rest of the metal on that tongue, a welding shop can probably cut out the bad section and replace it. But...from the look of it, I'll bet you have internal corrosion elsewhere on the tongue.
How is the rest of the trailer? Lots of rust? If so, it's time to junk it and get a new one. If the rest is sound, just have the tongue replaced or a new section welded in, with bracing.
The welding shop can advise you best after seeing the situation as a whole.