Reading the PHB, DM, and MM, I am having a hard time understanding how healing works for necrotic damage done by the attacks of various undead, such as the Vampire's Bite attack on page 297 of the Monster Manual. I think what happens is not terribly well explained. It says:
[…] plus 10 (3d6) necrotic damage. The target's hit point maximum is reduced by an amount equal to the necrotic damage taken, […]. The reduction lasts until the target finishes a long rest.
It seems like, after being bitten by a vampire, a PC can recover all hit points after a long rest, but Cure Wounds can't restore these lost hit points sooner due to only being able to restore hit points up to the new (reduced) maximum. That seems really weird to me.
Can Cure Wounds or other magical healing (e.g., Lay On Hands) really not restore hit points lost to the vampire's bite?