One should hold Bachelor degree in any subject with 50% marks or equivalent CGPA.the candidates belonging to scheduled castes or scheduled tribes need only 45% marks. The students in the final year can also apply for the CAT exam.
CAT prescribes no Age bar to allow students of every sort to appear for the exam.

for the further details, you can go to the given below link 
https://bschool.careers360.com/articles/cat-eligibility-criteria