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Researchers Disclose Unpatched Flaws in Schneider Electric PLCs

Researchers have disclosed the details of two vulnerabilities affecting some of Schneider Electric’s Modicon programmable logic controllers (PLCs) after the vendor failed to provide any status updates or feedback.

Researchers have disclosed the details of two vulnerabilities affecting some of Schneider Electric’s Modicon programmable logic controllers (PLCs) after the vendor failed to provide any status updates or feedback.

A team of experts from Germany-based OpenSource Security discovered the flaws in Schneider’s Modicon M221 PLCs, namely TM221CE16R running firmware version

According to advisories published on Tuesday by the researchers, the vulnerabilities are critical and they can be easily exploited.

One of the flaws is related to the fact that the Project Protection feature, designed to prevent unauthorized access to project files, uses a hardcoded encryption key.

The project’s password is stored in an XML file that is encrypted using the AES algorithm in CBC mode. The problem is that the encryption key is the same for all systems and it cannot be changed, allowing an attacker to decrypt the XML file and obtain the password set by the user.

The password can then be used to access and modify a project via SoMachine Basic, the software designed for programming Modicon controllers.

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The second vulnerability is related to the Application Protection feature, which prevents the transfer of an application from a PLC to a SoMachine Basic project. Researchers discovered that sending a simple command via Modbus to the controller on TCP port 502 will return the Application Protection password in clear text.

The password can be used via the SoMachine software to download applications from the controller, modify them and upload them back to the device.

The researchers said they reported their findings to Schneider Electric on December 23, but the only information they got from the vendor was the confirmation that the vulnerability report had been received.

Contacted by SecurityWeek, Schneider Electric admitted making a mistake and promised to share mitigation advice for these flaws as soon as possible on its cybersecurity support portal.

“Schneider Electric acknowledges the security note on its product Modicon TM221CE16R, Firmware, disclosed by OpenSource Security,” the company said in an emailed statement.

“Conscious about user Cyber Security concerns, Schneider Electric places a high priority on the evaluation of security research as it becomes available and produces documentation to advise users on mitigations that can be taken if they are required. Because of an issue in our standard process for interactions with cybersecurity advisory & consulting firms, we have missed the opportunity to respond to the researchers from OpenSource Security (Simon Heming, Maik Brüggemann, Hendrik Schwartke, Ralf Spenneberg) and offer mitigation to users, and we do apologize for this. We’re reviewing and updating our processes to make sure such a situation never happens again,” the company added.

Schneider Electric recently notified customers about the availability of patches and mitigations for three vulnerabilities affecting some of its Modicon PLCs.

Related: High Severity Flaws Patched by Siemens, Schneider Electric

Related: Schneider Electric Patches Flaws in ClearSCADA, Wonderware Products

Related: Flaw in Schneider Industrial Firewalls Allows Remote Code Execution

Written By

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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