What is the journal entry for the cash stolen from cash box?

Debit: Profit & Loss Account

Credit: Cash In Hand or Petty Cash

Nature of Debit is Expense and the nature of Credit is Asset.

Expense Increased and Asset Decreased

If you have an account already open for such Losses then you should debit such account. For example in my company Cash loss is usual Case so we have an Account titled "Cash Lost Expense"

In my cash I will pass the entry as

Debit: Cash Lost Expense

Credit: Cash in Hand or Petty Cash