DoS vulnerability in Siemens S7-1200 PLCs

From: Arne Vidström <>
To: <>
Subject: DoS vulnerability in Siemens S7-1200 PLCs

Hi all,

I have found a DoS vulnerability in the Siemens S7-1200 PLCs. It is present in firmware versions 2 and 3. After an exchange of specially crafted packets to TCP port 102 the PLC shuts down. The red, green and yellow status LEDs start flashing. All outputs are shut off. The device stops listening at port 102 and becomes completely non-responsive. Sometimes a few status messages are sent before it shuts down. They state that a serious firmware error has occurred and that the PLC is defective. Power cycling the PLC restores operation though.

More information can be found in the Siemens advisory:

Best regards /Arne


Arne Vidstrm
Swedish Defence Research Agency (FOI)

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