Cardio isn't necessary for fat loss, but it could help — it depends on the individual.
Dimitri said, "If your weight training sessions (especially legs) are intense enough to challenge you" and you're consuming your goal intake of daily calories, this will usually be enough to prevent fat gain. If it isn't, try adding one to two additional cardio sessions. They don't have to be very long. They can be short and intense, such as HIIT sessions.
Image Source: POPSUGAR Photography / Diggy Lloyd