The CFA is pass/fail in terms of determining whether or not you are physically qualified for admission. However, in response to what AmericanFKP12 said above, the CFA makes up 10% of your WCS. So, candidates that score higher on the CFA will be given more points for this section of their WCS. If there is one offer of appointment left, and it is down to you and one other candidate who are equal in every regard except your CFA, and you scored higher than them, then you will receive the offer. Thus, while it is necessary to pass the CFA in order to be fully qualified for admission, you should aim for the highest scores possible.