Data::RadixTree::Shared versions before 0.02 for Perl allow an out-of-bounds read via unvalidated node and arena indices in rdx_find_locked

Data::RadixTree::Shared versions before 0.02 for Perl allow an out-of-bounds read via unvalidated node and arena indices in rdx_find_locked. The attach-time validator rdx_validate_header checks the header scalars and region layout against the file size, but does not validate the node records it then trusts. rdx_find_locked indexes nodes[cur].children[k] and reads each node's label_off and label_len raw from the mmap'd segment, none bounded against the node count or the arena size. A local peer that can write the backing file can leave the header valid while poisoning the node records, so a lookup dereferences an out-of-bounds node or arena index, reading adjacent memory or crashing the process.