Vulnerability Exposes Rockwell Controllers to DoS Attacks

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Some of Rockwell Automation’s MicroLogix controllers and ControlLogix communications modules are affected by a potentially serious vulnerability that can be exploited for denial-of-service (DoS) attacks.

ICS-CERT published an advisory describing the vulnerability on Thursday, but Rockwell Automation informed customers of the flaw several weeks ago – Rockwell’s advisory is only available to registered users.

According to Rockwell and ICS-CERT, the security hole, tracked as CVE-2018-17924 with a CVSSv3 score of 8.6, impacts MicroLogix 1400 controllers from the A, B and C series. It also affects various versions of the 1756 ControlLogix Ethernet/IP communications modules, including series A, B, C and D.

ICS-CERT says the impacted products are used worldwide in sectors such as transportation, critical manufacturing, food and agriculture, and water and wastewater.

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The vulnerability allows a remote and unauthenticated attacker to cause the impacted devices to enter a DoS condition.

“An unauthenticated, remote threat actor could potentially send a CIP connection request to an affected device and, upon successful connection, send a new IP configuration to the affected device even if the controller in the system is set to Hard RUN mode,” Rockwell explained. “When the affected device accepts this new IP configuration, a loss of communication occurs between the device and the rest of the system. Reason being, the system traffic is still attempting to communicate with the device via the IP address that was overwritten.”

Rockwell has released firmware updates for some of the affected controllers and communications modules, but for many of them it has only provided mitigations.

These mitigations include using firewalls to block Ethernet/IP messages from unauthorized sources, using hardware keyswitch settings to prevent unauthorized changes to the device, and minimizing network exposure to control systems.

DoS vulnerabilities can pose a serious risk in industrial environments as they can be exploited to cause severe disruptions to production systems. In contrast to IT networks, where confidentiality is the most important, the biggest concern for OT network operators is availability.

Related: Rockwell Patches Flaw Affecting Safety Controllers From Several Vendors

Related: Severe Vulnerabilities Expose MicroLogix PLCs to Attacks

Related: Rockwell Automation Patches Severe Flaws in Communications Software

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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.

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