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Schneider Electric has mitigations available to handle an improper check for unusual or exceptional conditions vulnerability in its Modicon Controllers, according to a report with NCCIC.

Successful exploitation of this remotely exploitable vulnerability, discovered by Zhang Xiaoming, Zhang Jiawei, Sun Zhonghao and Luo bing of CNCERT/CC, could result in a denial-of-service condition.

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The following versions of Modicon Controllers, a PLC and PAC controller for industrial control systems, suffer from the issue:
• Modicon M340: Firmware versions prior to v3.01
• Modicon M580: Firmware versions prior to v2.80
• Modicon Quantum: All firmware versions
• Modicon Premium: All firmware versions

An attacker could create a denial-of-service condition by sending a specific crafted Modbus frame to the affected device.

Cyber Security

CVE-2019-6819 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 7.5.

The product sees use in multiple sectors and on a global basis.

No known public exploits specifically target this vulnerability. However, an attacker with low skill level could leverage the vulnerability.

Schneider Electric recommended the following to mitigate this vulnerability.

Modicon M340 – The vulnerability is fixed in v3.01 and is available for download.

BMXP3420302 and CL and H
BMXP342020 and H
BMXP342000
BMXP341000 and H
BMXP3420102 and CL
BMXP3420302 and H

Modicon M580 – The vulnerability is fixed in v2.80 and is available for download below:
BMEP584040, BMEP584040S, BMEH584040 and C
BMEP586040 and C
BMEH586040 and C
BMEP581020 and H
BMEP582020 and H
BMEP582040 and H
BMEP583020
BMEP583040
BMEP584020
BMEP585040 and C
BMEP582040S
BMEH582040 and C

Schneider Electric’s Modicon Quantum controllers have reached the end of their life and are no longer commercially available. They have been replaced by the Modicon M580 ePAC controller, Schneider Electric’s most current product. Schneider Electric recommends users migrate to the Modicon M580 ePAC.

To mitigate risks associated with this Modbus vulnerability, users should immediately set up network segmentation and implement a firewall to block all unauthorized access to Port 502/TCP.

Schneider Electric general security recommendations:
• Locate control and safety system networks and remote devices behind firewalls, and isolate them from the business network.
• Physical controls should be in place so no unauthorized persons have access to the ICS and safety controllers, peripheral equipment, or the ICS and safety networks.
• All controllers should reside in locked cabinets and never be left in the “Program” mode.
• All programming software should be kept in locked cabinets and should never be connected to any network other than the network for the intended devices.
• All methods of mobile data exchange with the isolated network (e.g., CDs, USB drives, etc.) should be scanned before use in the terminals or any node connected to these networks.
• Laptops that have connected to any other network besides the intended network should never be allowed to connect to the safety or control networks without proper sanitation.
• Minimize network exposure for all control system devices and/or systems, and ensure they are not accessible from the Internet.
• When remote access is required, use secure methods, such as virtual private networks (VPNs), recognizing that VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize VPN is only as secure as the connected devices.

For more information, please see Schneider Electric advisory.

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