That tends to be a general problem with human societies, and as Cowbee points out there's nothing about communism that makes society more prone to corruption. If anything, I'd argue it's the opposite since you have less inequality. In general, I look at corruption as a form of inefficiency. So, a government that has corruption, but works in the interests of the majority overall is still a better scenario than one that works in the interest of a capital owning minority.