Possession, undead and positive / negative energy

[Myrryr]

So, an interesting thing came up in a session today and apparently google was not able to find me an answer.
What happens when you cast a cure spell on a living person who's possessed by an undead? (Ghost, lich with magic jar, doesn't matter really) Does the undead creature feel any feedback at all? Positive energy can affect incorporeal creatures, regardless of whether or not they're inside a solid object, even if it's at half-damage (barring effects like Ghostbane Dirge), but generally speaking a possessed creature is the target of spells and effects unless they say they'll affect a possessing creature, such as Protection from Evil being able to force them out.

[Claxon]

Pretty sure it would just heal the host.

Just like fireball only damages the host body, healing spells will only affect the host as well.