Immune to Poison and Disease: Unaffected by poisons and cannot be inflicted with any disease

Undead Fortitude. If damage reduces the Undead Wolf to 0 hit points, it must make a Constitution saving throw with a DC of 7 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 2) piercing damage. If the target is a creature, it must succeed on a DC 11 Strength saving throw or be knocked prone.