CVE-2021-43083 in PLC4X - PLC4C
Summary
by MITRE • 12/19/2021
Apache PLC4X - PLC4C (Only the C language implementation was effected) was vulnerable to an unsigned integer underflow flaw inside the tcp transport. Users should update to 0.9.1, which addresses this issue. However, in order to exploit this vulnerability, a user would have to actively connect to a mallicious device which could send a response with invalid content. Currently we consider the probability of this being exploited as quite minimal, however this could change in the future, especially with the industrial networks growing more and more together.
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Analysis
by VulDB Data Team • 12/24/2021
The vulnerability identified as CVE-2021-43083 affects Apache PLC4X's PLC4C implementation, which is a C language library designed for industrial communication protocols. This flaw manifests within the TCP transport layer functionality that handles communication between industrial control systems and PLC4X clients. The issue represents a critical security concern as it involves an unsigned integer underflow condition that can potentially lead to unpredictable behavior and system instability. The vulnerability specifically impacts the C language implementation of PLC4X, while other language variants remain unaffected, highlighting the targeted nature of the flaw within the software ecosystem.
The technical exploitation of this vulnerability occurs through an unsigned integer underflow within the TCP transport mechanism of the PLC4C library. This type of flaw falls under CWE-191, which specifically addresses unsigned integer underflow conditions that can result in unexpected program behavior. When a malicious device attempts to establish communication with a vulnerable PLC4C client, it can send malformed responses that trigger the underflow condition. The underflow occurs when an unsigned integer operation results in a value that cannot be represented within the unsigned integer type, potentially causing memory corruption or arbitrary code execution. This vulnerability demonstrates how industrial communication protocols can be susceptible to classic software security flaws that are well-documented in cybersecurity literature.
The operational impact of this vulnerability extends beyond simple software instability to potentially compromise industrial control systems that rely on PLC4X for communication. The exploitation requires an active connection from a malicious device, which creates a specific attack vector that must be carefully considered in industrial network security assessments. The risk assessment indicates a minimal probability of exploitation at present, yet this assessment must evolve as industrial networks become increasingly interconnected and exposed to external threats. Organizations implementing PLC4X in industrial environments face potential risks that could affect operational technology systems, particularly when these systems are connected to broader network infrastructures that may be compromised.
The recommended mitigation strategy involves updating to version 0.9.1 of the PLC4X library, which includes patches specifically addressing the unsigned integer underflow condition. This update represents a standard remediation approach that aligns with industry best practices for vulnerability management and software maintenance. Organizations should implement this update as part of their regular patch management procedures, particularly given the critical nature of industrial control systems. The vulnerability's classification within the ATT&CK framework would likely fall under techniques related to privilege escalation and execution of malicious code within industrial environments. Security teams must consider this vulnerability as part of broader industrial cybersecurity frameworks, ensuring that their defensive measures account for both traditional IT security concerns and the unique challenges presented by operational technology environments. The interconnected nature of modern industrial networks means that vulnerabilities in communication libraries like PLC4C can potentially serve as entry points for more sophisticated attacks targeting critical infrastructure systems.