Can disarm, trip, and sunder auto confirm?

[CyraxR]

I have a player who's character is focused on disarming and tripping the enemy. So his bonuses are to the point at level five that to defend against him the enemy has to be impossibly higher level then him or trained against disarm and trip. I have made an enemy that is the second of the two possibles with a CMD high enough that a nat twenty has to auto confirm to beat it. Now the question is do disarm, trip,(the important ones here) and sunder attempts auto confirm with a nat twenty?

[Jiggy]

As per Core Rules (specifically the Combat chapter), combat maneuvers automatically succeed on a natural 20 and automatically fail on a natural 1.

[Grick]

CyraxR wrote:

do disarm, trip,(the important ones here) and sunder attempts auto confirm with a nat twenty?

A Combat Maneuver is an attack roll.

Automatic Misses and Hits: "A natural 1 (the d20 comes up 1) on an attack roll is always a miss. A natural 20 (the d20 comes up 20) is always a hit."

Critical Hits: "When you make an attack roll and get a natural 20 (the d20 shows 20), you hit regardless of your target's Armor Class, and you have scored a “threat,” meaning the hit might be a critical hit (or “crit”). To find out if it's a critical hit, you immediately make an attempt to “confirm” the critical hit—another attack roll with all the same modifiers as the attack roll you just made. If the confirmation roll also results in a hit against the target's AC, your original hit is a critical hit. (The critical roll just needs to hit to give you a crit, it doesn't need to come up 20 again.) If the confirmation roll is a miss, then your hit is just a regular hit."

Since a natural 20 is always a hit, rolling a natural 20 on the confirmation roll will automatically confirm.

[Quandary]

also remember: fliers are immune to trip (swimmers and burrowers should probably be as well, though not per RAW), multi-legged creatures (and other special cases like creatures without legs) get bonuses vs. trip, as do dwarves and other creatures with 'stability', and of course monsters/NPCs with natural weapons can't be disarmed. that's all pretty much standard stuff, especially if you have 5th level PCs. going to the length of making only-succeed-on-20 enemies doesn't seem like it necessary... although i suppose the best way to do it is to take those improved CMB feats themself, so they may be fighting back with the same medicine, which can be nice to try out.

there's some rogue talents that allow getting up from prone without AoO and as a free action or something like that, as another angle to take to mix up the enemies.