  FT_Stream_ReadAt( FT_Stream  stream,
                    FT_ULong   pos,
                    FT_Byte*   buffer,
                    FT_ULong   count )
  {
    FT_Error  error = FT_Err_Ok;
    FT_ULong  read_bytes;


    if ( pos >= stream->size )
    {
      FT_ERROR(( "FT_Stream_ReadAt:"
                 " invalid i/o; pos = 0x%lx, size = 0x%lx\n",
                 pos, stream->size ));

      return FT_Err_Invalid_Stream_Operation;
    }

    if ( stream->read )
      read_bytes = stream->read( stream, pos, buffer, count );
    else
    {
      read_bytes = stream->size - pos;
      if ( read_bytes > count )
        read_bytes = count;

      FT_MEM_COPY( buffer, stream->base + pos, read_bytes );
    }

    stream->pos = pos + read_bytes;

    if ( read_bytes < count )
    {
      FT_ERROR(( "FT_Stream_ReadAt:"
                 " invalid read; expected %lu bytes, got %lu\n",
                 count, read_bytes ));

      error = FT_Err_Invalid_Stream_Operation;
    }

    return error;
  }

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.