OSV-2020-531 Stack-buffer-overflow in ot::MeshCoP::DatasetManager::HandleSet

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15374 Crash type: Stack-buffer-overflow READ 15 Crash state: ot::MeshCoP::DatasetManager::HandleSet ot::MeshCoP::ActiveDataset::HandleSet ot::Coap::CoapBase::ProcessReceivedRequest...