The short answer is: Yes
By definition, all cult members are gullible. They are gullible for believing the myths and lies which persuade them to join in the first place. That should be obvious.
Even Born-ins probe themselves to be gullible if they continue to believe after more than a few years of adult life and experience.
Of course the psychology behind joining and/or remaining in a cult is much more complex than my simplistic response might seem to suggest.
But the question in the OP was not that subtle: it was direct and straightforward and so is my answer.