int CopyBaseDriveSpecIfNecessary(const char* base_url,
                                 int base_path_begin,
                                 int base_path_end,
                                 const CHAR* relative_url,
                                 int path_start,
                                 int relative_url_len,
                                 CanonOutput* output) {
  if (base_path_begin >= base_path_end)
    return base_path_begin;  // No path.

  if (url_parse::DoesBeginWindowsDriveSpec(relative_url,
                                           path_start, relative_url_len)) {
    return base_path_begin;  // Relative URL path is "C:/foo"
  }

  if (DoesBeginSlashWindowsDriveSpec(base_url,
                                     base_path_begin,
                                     base_path_end)) {
    output->push_back('/');
    output->push_back(base_url[base_path_begin + 1]);
    output->push_back(base_url[base_path_begin + 2]);
    return base_path_begin + 3;
  }

  return base_path_begin;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.