CVE-2019-10953

Summary

ABB, Phoenix Contact, Schneider Electric, Siemens, WAGO - Programmable Logic Controllers, multiple versions. Researchers have found some controllers are susceptible to a denial-of-service attack due to a flood of network packets.

Affected Software

Weaknesses

• CWE-400: UNCONTROLLED RESOURCE CONSUMPTION CWE-400

Workarounds

ABB concludes the reported behavior is not a vulnerability but is due to a misconfiguration of the PLC watchdog, which was left in the default factory settings. This has led to a configuration that does not match the expectations expressed in the test cases and the result is the PLC not reacting as intended. This misconfiguration can be fixed by setting an appropriate combination of task priority, task cycle time, and watchdog settings. Please see the “Onboard Ethernet Handling in CPU Firmware” chapter (System Technology for AC500 V2 Products > System Technology of CPU and Overall System > Onboard Technologies > Ethernet > Ethernet Protocols and Ports for AC500 V2 Products > Onboard Ethernet Handling in CPU Firmware) for further guidance. Phoenix Contact acknowledges this as a “known, won’t fix” issue for old products. Currently available products provide countermeasures to mitigate the impact on the safety-related functionality. Phoenix Contact urges users to adhere to the Application note 107913_en_01.

More information can be found in the  VDE CERT advisory https://cert.vde.com/en-us/advisories/vde-2018-012 . Siemens has investigated the vulnerability report on PLC cycle time influences and concludes the report does not demonstrate a valid vulnerability for Siemens PLCs. WAGO recommends users operate the devices in closed networks or protect them with a firewall against unauthorized access. Another recommended mitigation is to limit network traffic via the switch rate limit feature according to application needs. Please also consult the product manuals on the WAGO website, as this is a known problem for some devices. Links to product manuals and specific instructions about how to limit switch rates can be found in the  VDE CERT advisory https://cert.vde.com/de-de/advisories/vde-2018-013 .

ADP Enrichment

CVE Program Container

Additional References

• https://ics-cert.us-cert.gov/advisories/ICSA-19-106-03
• http://www.securityfocus.com/bid/108413

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: yes
  • Technical Impact: partial

References

• https://ics-cert.us-cert.gov/advisories/ICSA-19-106-03
• http://www.securityfocus.com/bid/108413
• https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2019/icsa-19-106-03.json

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