While not a new weapon model, v48738 introduces a new for the Tactical Axe. If you revisit the abandoned campsite near the snowy mountain pass, you can find a rusted axe head etched with Nordic-style runes.
If you own the game legitimately on Steam, your copy auto-updates — no need for RUNE releases. sons of the forest update v48738rune new
There is no official record of a Sons of the Forest update specifically numbered v48738rune Sons of the Forest Update v48738: What's New