Security Experts:

Siemens SCALANCE X Switches Vulnerable to DoS Attacks

Siemens on Tuesday released several new advisories describing vulnerabilities in the company’s products, including an unpatched denial-of-service (DoS) flaw affecting SCALANCE X industrial switches.

According to advisories published by Siemens and the DHS’s Cybersecurity and Infrastructure Security Agency (CISA), SCALANCE X-200 switches are affected by a security hole that allows an unauthenticated attacker to cause a device to enter a DoS condition by repeatedly sending large message packets to the Telnet service.

The vulnerability was reported to Siemens by industrial cybersecurity firm Nozomi Networks.Siemens SCALANCE X switch vulnerabilities

“The vulnerability affects the telnet server, allowing an attacker to crash the service by sending a large number of packets on the port 23/TCP,” Andrea Carcano, CPO and co-founder of Nozomi Networks, told SecurityWeek. “After the crash, the device is automatically restarted, disconnecting from the network all the connected devices; this can lead to a potential process disruption.”

While exploitation of this vulnerability would require access to the network housing the targeted switches, Carcano said Nozomi’s intelligence team has identified a couple of devices that may be exposed to attacks launched directly from the internet.

As for how difficult it is to exploit this vulnerability, Carcano noted, “The attacker does not need any understanding about specific protocols or systems, just some knowledge of the standard telnet protocol.” However, he said, “The vulnerability is not easy to exploit as it could have a non-deterministic replication step to take in order to trigger it.”

Siemens has yet to release any patches for the vulnerability, which it has classified as “high severity,” but the company has informed customers that they can prevent potential attacks by disabling the Telnet service on affected devices (using SSH instead is recommended), and restricting network access to TCP port 23.

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The German industrial giant also informed customers on Tuesday that its SCALANCE X switches and SCALANCE SC firewalls are affected by two medium-severity flaws that can be exploited for DoS attacks and arbitrary command execution. However, exploitation requires authentication and, for one of the vulnerabilities, physical access to the targeted device.

Siemens has also published an advisory in response to a Black Hat presentation describing how rogue engineering stations can be used to take control of some S7 programmable logic controllers (PLCs).

Finally, Siemens released an advisory describing a high-severity DoS vulnerability impacting the web server of SINAMICS converters. The flaw allows an attacker with network access to the affected system to cause a DoS condition without the need for authentication or user interaction.

Related: Siemens Teams With Chronicle on Cybersecurity Solutions for Energy Industry

Related: Siemens Patches Serious DoS Flaws in Many Industrial Products

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.