SEC Consult Vulnerability Lab Security Advisory < 20211028-0 > ======================================================================= title: CODESYS V2 Denial of Service product: CODESYS Runtime Toolkit 32-bit, CODESYS PLCWinNT vulnerable version: <V2.4.7.56 fixed version: V2.4.7.56 CVE number: CVE-2021-34593 impact: High homepage: https://www.codesys.com/ found: 2021-05-05 by: SEC Consult Vulnerability Lab This vulnerability was discovered during the research cooperation initiative "OT Cyber Security Lab" between Verbund AG and SEC Consult Group. Gerhard Hechenberger (Office Vienna) Steffen Robertz (Office Vienna) An integrated part of SEC Consult, an Atos company Europe | Asia | North America https://www.sec-consult.com ======================================================================= Vendor description: ------------------- "CODESYS is the leading manufacturer-independent IEC 61131-3 automation software for engineering control systems." Source: https://www.codesys.com/ Business recommendation: ------------------------ The vendor provides patches. The vendors of products using the affected software should provide new firmware versions immediately. Users of these products should update their devices to those fixed firmware versions. Vulnerability overview/description: ----------------------------------- The CODESYS Control runtime system is the core of many PLCs. The runtime is accepting TCP connections on a pre-configured port to connect to the development system. By sending requests that define an invalid packet size, a memory allocation error can be triggered. This leads to a denial of service condition of the remote connectivity of the CODESYS service, which prevents clients from connecting to the affected PLC. CODESYS released a dedicated security note, which corresponds to this advisory: https://customers.codesys.com/index.php?eID=dumpFile&t=f&f=16877&token=8faab0fc1e069f4edfca5d5aba8146139f67a175 Proof of concept: ----------------- A detailed proof of concept will be made public after the affected product vendors had time to provide new firmware versions. Vulnerable / tested versions: ----------------------------- 2.4.7.0 Vendor contact timeline: ------------------------ 2021-05-25: Contacting 3rd party vendor of a product using the CODESYS runtime about this issue. 2021-08-11: Vendor states that this issue was already fixed in a recent CODESYS release. 2021-08-18: A check on the product's most recent public firmware release shows that the vulnerability still exists. The vendor is notified again about this outcome. 2021-09-01: The vendor confirms and ensures the issue is investigated in collaboration with CODESYS. 2021-10-15: CODESYS informs about the assigned CVE-2021-34593 and the planned publishing date. 2021-10-28: Coordinated release. Solution: --------- Immediately update to the patched version of CODESYS. Workaround: ----------- To mitigate this issue, access to the CODESYS service port of the affected devices should be limited as far as possible. In the long run, the updated firmware of the product vendor containing a patched CODESYS service must be installed. Advisory URL: ------------- https://sec-consult.com/vulnerability-lab/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SEC Consult Vulnerability Lab SEC Consult, an Atos company Europe | Asia | North America About SEC Consult Vulnerability Lab The SEC Consult Vulnerability Lab is an integrated part of SEC Consult, an Atos company. It ensures the continued knowledge gain of SEC Consult in the field of network and application security to stay ahead of the attacker. The SEC Consult Vulnerability Lab supports high-quality penetration testing and the evaluation of new offensive and defensive technologies for our customers. Hence our customers obtain the most current information about vulnerabilities and valid recommendation about the risk profile of new technologies. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Interested to work with the experts of SEC Consult? Send us your application https://sec-consult.com/career/ Interested in improving your cyber security with the experts of SEC Consult? Contact our local offices https://sec-consult.com/contact/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Mail: research at sec-consult dot com Web: https://www.sec-consult.com Blog: http://blog.sec-consult.com Twitter: https://twitter.com/sec_consult EOF Gerhard Hechenberger, Steffen Robertz / @2021