Rockwell Fixes MicroLogix Holes

Tuesday, May 23, 2017 @ 03:05 PM gHale


Rockwell Automation released a new firmware version for the Allen-Bradley MicroLogix 1400 Series B controllers, and created compensating controls for its MicroLogix 1100 or MicroLogix 1400 Series A controllers, according to a report with ICS-CERT.

These remotely exploitable vulnerabilities came to ICS-CERT by Rockwell Automation, David Formby and Raheem Beyah of Georgia Tech and Fortiphyd Logic, Inc. Rockwell Automation also reported a vulnerability initially identified by Ilya Karpov of Positive Technologies.

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The vulnerabilities include predictable value range from previous values; reusing a nonce, key pair in encryption; information exposure; improper restriction of excessive authentication attempts, and weak password requirements.

The following versions of the Allen-Bradley MicroLogix 1100 programmable-logic controller suffer from the issues:
• 1763-L16AWA, Series A and B, Version 16.00 and prior versions
• 1763-L16BBB, Series A and B, Version 16.00 and prior versions
• 1763-L16BWA, Series A and B, Version 16.00 and prior versions
• 1763-L16DWD, Series A and B, Version 16.00 and prior versions

The following versions of the Allen-Bradley MicroLogix 1400 programmable logic controller suffer from the issues:
• 1766-L32AWA, Series A and B, Version 16.00 and prior versions
• 1766-L32BWA, Series A and B, Version 16.00 and prior versions
• 1766-L32BWAA, Series A and B, Version 16.00 and prior versions
• 1766-L32BXB, Series A and B, Version 16.00 and prior versions
• 1766-L32BXBA, Series A and B, Version 16.00 and prior versions
• 1766-L32AWAA, Series A and B, Version 16.00 and prior versions

Successful exploitation of these vulnerabilities may allow a remote attacker to gain unauthorized access to the affected programmable logic controllers and to spoof or disrupt TCP connections.

Insufficiently random TCP initial sequence numbers are generated, which may allow an attacker to predict the numbers from previous values. This may allow an attacker to spoof or disrupt TCP connections, resulting in a denial of service for the target device.

CVE-2017-7901 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 5.4.

The affected product reuses nonces, which may allow an attacker to capture and replay a valid request until the nonce is changed.

CVE-2017-7902 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 5.4.

In another vulnerability, user credentials are sent to the web server using the HTTP GET method, which may result in the credentials being logged. This could make user credentials available for unauthorized retrieval.

CVE-2017-7899 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 3.1.

In addition, there are no penalties for repeatedly entering incorrect passwords.

CVE-2017-7898 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 9.8.

Another vulnerability has the affected products using a numeric password with a small maximum character size for the password.

CVE-2017-7903 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 9.8.

The products see use in the food and agriculture and the water and wastewater system sectors. They also see action on a global basis.

No known public exploits specifically target these vulnerabilities. An attacker with low skill level can leverage the vulnerabilities.

Milwaukee, WI-based Rockwell Automation released a new firmware version for the Allen-Bradley MicroLogix 1400 Series B controllers, FRN 21.00, to address the identified vulnerabilities. Rockwell Automation encourages users to apply the latest firmware versions that address the identified vulnerabilities.

Rockwell Automation’s new firmware version for the Allen-Bradley MicroLogix 1400 Series B controllers, FRN 21.00, is available.

There are no firmware versions to address these vulnerabilities in the Allen-Bradley MicroLogix 1100 or MicroLogix 1400 Series A controllers, but Rockwell Automation has offered some compensating controls. Rockwell Automation reports that users can disable the web server on the Allen-Bradley MicroLogix 1100 and 1400 Series A controllers to protect against the exploitation of the improper restriction of excessive authentication attempts and weak password requirements vulnerabilities.

Rockwell Automation recommends that if it is not needed, users should consider disabling the web server to further mitigate these threats.
• Disable the web server on the MicroLogix 1100 and 1400 controllers, if not needed, as it is enabled by default. See Knowledge Base article: 732398 for detailed instructions on disabling the web server. The Web Server Tech Note, KB: 732398 – How to Disable the Web Server in MicroLogix 1100 and 1400 is available at the following URL with a valid account.
• Set the mode to RUN via LCD soft keyswitch to prohibit any re-enabling of the web server while the keyswitch is in this mode.



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