Keen Smell. The bear has advantage on Wisdom (Perception) checks that rely on smell.

Undead Fortitude. If damage reduces the zombie to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead.

Zombie infection. If a target takes poison damage from this creature the target must succeed a DC 8 Constitution Save every day until it passes or fails 3 saves. On 3 fails the target becomes a Zombie, on 3 successes the effect ends.

Multiattack. The bear makes two attacks: one with its infectious bite and one with its claws.

Infectious Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) piercing damage. On a hit the target must make a DC 12 Constitution save or take an additional 3 (1d6) poison damage and is (poisoned).

Claws. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage.