Intake and exhaust into the same room.

The cabinet is very small, 18" L x 14" W x 28" H. I will be doing a scrog grow with CFLs. It has to be a stealth grow, so my options are very limited.
The cabinet is close to my Window AC unit, I can keep the area around the cabinet very cold.

Intake air:
It will be passive intake, taking air from the room into the cabinet by using a exhaust fan taking air out of the sealed cabinet.

Exhaust air:
It will be an fan pulling air from inside the cabinet out.

Odor control:
It will be a carbon filter(maybe DIY) connected to the exhaust fan.

My concerns:
Iam exhausting air from inside the cabinet into the same room as my intake air. So the same cold air will be cycled through the cabinet, I can always open a window to allow a supply of fresh air into the room. Will I be fine with this setup?

You should be fine for a grow that size.
But, I would cut a small hole for intake.
Good luck

As long as you let fresh air into the room, it's ok. Plants will deplete the co2 in the air over time, but as it's a small grow it should take a while, unless the room it's in is very small.