Attack ranges for the mobs in this list may be incorrect:

• Cave spiders (Exactly 1 1/2 blocks off, completely impossible to attack in melee without being hit in almost all cases! This may be caused because a cave spider could attack the same distance as a regular spider while having a smaller size)
• Spiders (About 1 block off)
• Silverfish and endermites (About 1/2 a block off)
• Large slimes and large magma cubes (about 1 block off - 2016-12-26_21.12.44.png)
• Polar bears (Correct range, but they attempt to attack from too far)
• Baby polar bear (Attack range is way too high when hunting foxes; same problem as cave spider)
• Foxes (About 1/2 block off)
• Bees (About 1/2 block off)
• Pandas (About 1 block off)
• Dolphins (About 1 1/2 blocks off. Their attacks can be evaded if you fight them while sprint swimming or if you attack them at face level.)
• Ender dragons (Attack range varies. Don't know if this is a bug because it may be the wings that cause the damage and knockback.)
• Pufferfish (About 1 block off. Works as intended: MC-126163)
• Killer bunny (Unsupported mob that has the same attack range problem as cave spiders and baby polar bears. See MC-93038)

Use the shield to block attacks from these mobs and see how far they bump into the shield. If they bounce from the shield farther than they probably should, this may be a bug because all the other mobs have relatively correct attack ranges.

This is closely related to MC-2310, but not the same issue. This report here is about attack ranges for certain specific mobs being incorrect. MC-2310 is about the general detection whether a mob should be able to deal damage being incorrect.