This is normal behavior and all NetScaler appliances exhibit the same behavior.
To see the true extent of NetScaler CPU utilization, use the stat cpu command in the NetScaler CLI, or view NetScaler CPU utilization from the NetScaler GUI.

The NetScaler packet processing engine is always “looking for work”, even when there is no work to be done. Therefore, it will do everything it can to take control of the CPU and not release it.
On a server installed with NetScaler VPX and nothing else, this results in it looking like that NetScaler is consuming the entire CPU. Looking at the CPU utilization from “inside NetScaler” (by using the CLI or the GUI) provides a real picture of NetScaler CPU capacity being used.

When we execute top command on NetScaler, we see the outcome:

  PID USERNAME   THR PRI NICE   SIZE    RES STATE   C   TIME   WCPU COMMAND
 1163 root         1  44   r0  1291M  1292M CPU2    2 1643.1 100.00% NSPPE-01
 1164 root         1  44   r0  1291M  1292M CPU3    3 1643.1 100.00% NSPPE-02
 1162 root         1  44   r0  1292M  1292M CPU1    1 1643.1 100.00% NSPPE-00

Example showing stat cpu command for true value: 

Netscaler> stat cpu
CPU statistics
ID         Usage
1              1
 Done
Netscaler>