Yes, there have been various reported cases of fraud on the SAT. The most prominent two that come to mind are the recent college admissions scandal, in which strategies included both (1) having a substitute take the SAT in place of the student and (2) bribing the test proctor, and the year in which every test result from South Korea was canceled due to widespread cheating.

https://world.time.com/2013/05/10/for-the-first-time-sat-tes...