Research is performed in patients with age of ≥ 0 months old and < 31 years old. In course 1, sorafenib will be given orally (PO) on days 1 to 7. Pharmacokinetic studies on days 1 and 7 and pharmacodynamic assessment on day 8 will be performed. Inter-patient dose escalation or de-escalation of clofarabine and sorafenib will be performed based on tolerability and toxicity. On days 8 to 12, clofarabine and cytarabine will be administered intravenously (IV) without concurrent twice daily sorafenib. Sorafenib will then be given on days 15 to 28 (14 days). Cytarabine and clofarabine may be given before day 8 when the treating physician feels it is necessary after consulting with the primary investigator based on the participant's clinical condition (e.g. disease progression). Intrathecal (IT) methotrexate (age-adjusted doses) with leucovorin rescue (24 and 30 hours after IT therapy) can be given on day 8. Participants with central nervous system (CNS) disease can receive IT therapy weekly until the cerebrospinal fluid (CSF) becomes free of leukemia (minimum of 4 doses). Triple intrathecal therapy with methotrexate, hydrocortisone and cytarabine is allowed other than day 8 therapy.