CODESYS Denial Of Service

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  • CODESYS Runtime Toolkit 32-bit versions prior to suffer from a denial of service vulnerability.
    MD5 | 59e6a0e0191bcdaeb525d3aeaa31fe94

    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  
    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  
    Vendor description:  
    "CODESYS is the leading manufacturer-independent IEC 61131-3 automation  
    software for engineering control systems."  
    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:  
    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:  
    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  
    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.  
    Immediately update to the patched version of CODESYS.  
    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  
    Advisory URL:  
    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  
    Interested in improving your cyber security with the experts of SEC Consult?  
    Contact our local offices  
    Mail: research at sec-consult dot com  
    EOF Gerhard Hechenberger, Steffen Robertz / @2021  


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