Audition just records what is sent to it. There is no control over input levels. That needs to be done at the source, either using controls supplied with your audio interface or possibly in the Operating System's audio panel. What source are you recording that has such high levels?
I am using a virtual instrument. While it does have volume output controls, I was surprised to find that -- as you say -- Audition only records what is sent in to it. Are there any plans to implement such a control on Audition? Freeware/cheepware apps like GarageBand and Audacity have input level controls to avoid distortion from an incoming audio source, just like every Mackie mixer I've used has a trim/gain knob. My workaround now is to record in Audacity and then bring the wav/aiff files in to Audition for effects et al, but I wish I didn't have to do this.
By using a digital level control to adjust the level of an audio signal already in the digital domain reduces the bit depth. If you start with a 16 bit audio stream and reduce it's level by 12dB then you reduce the bit depth to the equivalnet of only 14 bits. Adjusting the levels in Garageband or Audacity is degrading the audio even before you start processing it. So it's best to get the levels correct at point of origin.