Yes you can. Here the response from the Linux Foundation:

The candidate will be provided with everything they need — including access to appropriate nodes, clusters, and required tools/binaries — to answer all questions on the exam. While they are free to install any Linux packages they wish via `apt`, should a candidate choose to install something not already available, they are on their own if something breaks as result. You may want to review the Exam Tips doc on https://www.cncf.io/certification/CKA/ to get understanding of how clusters are setup for the exam.