Monday, January 30, 2012

Siemens – The Big ICS-CERT Advisory

Today the DHS ICS-CERT folks published an unusual advisory. They combined reports of vulnerabilities from four separate researchers; Billy Rios, Terry McCorkle, Shawn Merdinger, and Luigi Auriemma; and combined them into one big (eleven separate vulnerabilities) advisory on the Siemens WinCC application. Not only is the big from the number of vulnerabilities, but the potential consequences of the exploitation of these vulnerabilities is really big. ICS-CERT notes that:

“Successful exploitation of these vulnerabilities could allow an attacker to log on to a vulnerable system as a user or administrator with the ability to execute arbitrary code or obtain full access to files on the system.”

Given the wide range of facilities that this Siemens application is used, an attacker would have a wide range of potential targets that could essentially be exploited at will, shutting down electrical transmission facilities, water treatment facilities, chemical plants, even automotive manufacturing facilities. Simultaneous attacks on a number of targets across a number of manufacturing and utility sectors could have a catastrophic impact on local, state, national, or even world economies.

The catalogue of vulnerabilities includes:

• Insecure authentications;
• Weak default passwords;
• Cross-site scripting;
• Header injection;
• Client-side attack;
• Lack of telnet daemon authentication;
• String stack overflow;
• Directory traversal (two separate vulnerabilities);
• Denials of Service; and
• Arbitrary memory read access.

The good news (and I’m really having to stretch here to call this ‘good news’) is that ONE of the vulnerabilities requires user interaction to exploit. Fortunately for Siemens’ customers there have been so few successful social engineering attacks over the last year or so (pardon the gross sarcasm). The bad news (and it doesn’t come much worse than this) is that there are publicly available exploits for 7 of the 11 (Oh Craps, I know, pardon the pun) vulnerabilities.

The good news (another stretch) is that Siemens has dealt with each of these vulnerabilities. They have

• Patched 5;

• Changed product documentation to explain how to correct one during set up;

• Recommended deactivation of transport mode for four others; and

• Explained that users have the option of disabling the final vulnerability.

The bad news is that no one outside of Siemens has verified if any of the above actions prevent the exploit of any of the eleven vulnerabilities included in this report.

The final good thing is that ICS-CERT put all of these vulnerabilities into a single advisory, making it easier to keep track of what has been fixed or not. It might be a good idea to do the same sort of thing for Siemen’s PLCs.

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