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[R1] 3S CODESYS PLCWinNT Runtime Service NULL Pointer Dereference Remote DoS



CODESYS Runtime, a runtime system that "turns any embedded or PC based device into a full-fledged IEC 61131-3 controller", is vulnerable to a remote denial of service attack. The issue is due to the PLCWinNT Runtime service that runs on TCP port 1200 not properly sanitizing user-supplied input. By sending a crafted request, a remote attacker can trigger a NULL pointer dereference, crashing the service. Without the service running, the functionality of the device is effectively gone. Tenable has created a working exploit that demonstrates the issue, but will not be releasing it.

Note that this Runtime system may be used in additional software.


Upgrade the PLCWinNT Runtime software to version, or upgrade to CODESYS which includes the updated Runtime.

Disclosure Timeline

2015-08-01 - Issue discovered
2015-08-04 - ICS-CERT informed, asked to coordinate and assign CVE
2015-08-10 - Tenable pinged ICS-CERT
2015-08-10 - ICS-CERT reply, ICS-VU-607305 assigned
2015-08-26 - ICS-CERT requests PoC on behalf of vendor, PoC sent
2015-08-27 - ICS-CERT relays PoC to vendor
2015-09-08 - Tenable pinged ICS-CERT re: CVE assignment
2015-10-12 - ICS-CERT indicates S3 plans to post a fix on 2015-10-15. Provides draft advisory with CVE ID for review.
2015-10-12 - Provided feedback on draft advisory
2015-10-15 - Issue disclosed via ICS-CERT, Vendor advisory, Tenable advisory (go coordination!)

All information within TRA advisories is provided “as is”, without warranty of any kind, including the implied warranties of merchantability and fitness for a particular purpose, and with no guarantee of completeness, accuracy, or timeliness. Individuals and organizations are responsible for assessing the impact of any actual or potential security vulnerability.

Tenable takes product security very seriously. If you believe you have found a vulnerability in one of our products, we ask that you please work with us to quickly resolve it in order to protect customers. Tenable believes in responding quickly to such reports, maintaining communication with researchers, and providing a solution in short order.

For more details on submitting vulnerability information, please see our Vulnerability Reporting Guidelines page.

If you have questions or corrections about this advisory, please email [email protected]

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