Noise in Arduino BLE Data Reading

The characters I got for Arduino BLE characteristics reading are always tailed with some random characters. For example, the printing should ends with "test string" but it actually print out "test string !" The tailing string is randomized based on different string being sent.

Any suggestions for resolving this issue?

The code for reading character is the following

void incomingCharacteristicWritten(BLEDevice central, BLECharacteristic characteristic) {
  byte value[characteristic.valueLength()];
  incomingDataCharacteristic.readValue(value, characteristic.valueLength());
  Serial.print("Characteristic event, written: ");
  Serial.print((char *) value);
}