"Ruth Strun Bah"

"Kren sosaal"

"Faaz nah"

Those are the ones I can think of.

Dragon exclamations are fundamentally different from human ones. The meaning of any word used as such must be relevant to the situation; there are no taboos per se.

Canonical examples include:

faaz lit. 'pain'
nah lit. 'fury'
ruth lit. 'rage'

Insults, too, carry meanings that would seem tame to less literal races:

nikriin 'coward'
daanik kendov 'doomed warrior'
mal lir 'little worm'
nivahriin joor 'cowardly mortal'

There's two types of swearing (in my opinion, there's no dictionary rule on swearing): exclamation and insultion. 

Exclamation could be things like 'ruth' which mean rage. 

An insult could be 'joor', which means mortal. 

But dragons wouldn't necessarily resort to profanity as such.