Memory exposure via uninitialized buffer passed to Read

Uninitialized memory use in csv-sniffer before 0.2.0 allows attackers to read process memory via a crafted Read implementation. The preamble_skipcount function passes an uninitialized buffer to a caller-supplied Read implementation, which can inspect the buffer or report an incorrect byte count. Exploitation requires a consuming application to supply an attacker-controlled Read implementation; effects are bounded to memory exposure and undefined behavior in that process.