Schneider Fixes Modicon PLC Issues

Friday, March 31, 2017 @ 01:03 PM gHale


Schneider Electric released new firmware to fix a series of vulnerabilities in its Modicon PLCs, according to a report with ICS-CERT.

The fix takes care of remotely exploitable predictable value range from previous values, use of insufficiently random values and insufficiently protected credentials vulnerabilities in the Modicon M221, M241 and M251 PLCs. David Formby and Raheem Beyah of Georgia Tech and Fortiphyd Logic, Inc. reported the identified vulnerabilities.

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The following versions of the Modicon M221, M241, and M251 PLCs suffer from a predictable value range from previous values vulnerability:
• Modicon M221, firmware versions prior to Version 1.5.0.0
• Modicon M241, firmware versions prior to Version 4.0.5.11
• Modicon M251, firmware versions prior to Version 4.0.5.11

The following versions of the Modicon M241 and M251 PLCs suffer from a use of insufficiently random values vulnerability:
• Modicon M241, firmware versions prior to Version 4.0.5.11
• Modicon M251, firmware versions prior to Version 4.0.5.11

The following versions of the Modicon M241 and M251 PLCs end up affected by an insufficiently protected credentials vulnerability:
• Modicon M241, all firmware versions
• Modicon M251, all firmware versions

Successful exploitation of these vulnerabilities may allow a remote attacker to spoof or disrupt Transmission Control Protocol (TCP) connections, sniff sensitive account information, and gain unauthorized access to a current web session.

In one vulnerability, the affected products generate insufficiently random TCP initial sequence numbers that may allow an attacker to predict the numbers from previous values. This may allow an attacker to spoof or disrupt TCP connections.

CVE-2017-6030 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 6.5.

In a use of insufficiently random values vulnerability, the session numbers generated by the web application are lacking randomization and are shared between several users. This may allow a current session to be compromised.

CVE-2017-6026 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 6.5.

In the insufficiently protected credentials vulnerability, log-in credentials end up sent over the network with Base64 encoding leaving them susceptible to sniffing. Sniffed credentials could then be used to log into the web application.

CVE-2017-6028 is the case number assigned to this vulnerability, which has CVSS v3 base score of 7.5.

The product line sees use in the critical manufacturing, food and agriculture and water and wastewater system sectors. The product line sees action on a global basis.

No known public exploits specifically target these vulnerabilities. However, an attacker with a low skill level would be able to leverage the vulnerabilities.

Schneider Electric released new firmware versions to address the predictable value range from previous values vulnerability and the use of insufficiently random values vulnerability, which are available through Schneider Electric’s software update tool, SoMachine, Version 4.2, and SoMachineBasic, Version 1.5. Schneider Electric has not released a product to address the insufficiently protected credentials vulnerability; however, Schneider Electric has provided compensating controls to reduce the risk of exploitation.

Click here to download SoMachineBasic, Version 1.5.

Schneider Electric provided the following compensating controls to reduce the risk of exploitation of the insufficiently protected credentials vulnerability:
• Verify the hardware and software infrastructure the PLCs are integrated into (along with all organizational measures and rules covering access to the infrastructure) consider the results of the hazard and risk analysis, and are implemented according to best practices and standards such as ISA/IEC 62443
• Limit traffic on the local network with managed switches
• Where possible, avoid using Wi-Fi networks, but when Wi-Fi is essential, use only secure communications (such as WPA2 encryption)
• Do not grant [network] access to unknown computers

When remote access is essential, use secure methods such as Virtual Private Networks (VPNs), and ensure the remote access solution(s), as well as the remote computer(s) are kept up-to-date with the latest security patches.

Schneider Electric released Security Notifications SEVD-2017-075-01, SEVD-2017-075-02, and SEVD-2017-075-03, which provide additional information about the identified vulnerabilities, mitigations, and compensating controls.



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