DoS vulnerability in Siemens S7-1200 PLCs

[Arne Vidström <arne.vidstrom@xxxxxx>]

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:

http://www.siemens.com/corporate-technology/pool/de/forschungsfelder/siemens_security_advisory_ssa-724606.pdf

Best regards /Arne

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Arne Vidström
Swedish Defence Research Agency (FOI)
http://www.foi.se/en/Our-Knowledge/Information-Security-and-Communication/Information-Security