CVE-2021-20607 in GX Works2
Summary
by MITRE • 12/17/2021
Integer Underflow vulnerability in Mitsubishi Electric GX Works2 versions 1.606G and prior, MELSOFT Navigator all versions and EZSocket all versions allows an attacker to cause a DoS condition in the software by getting a user to open malicious project file specially crafted by an attacker.
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Analysis
by VulDB Data Team • 12/24/2021
The integer underflow vulnerability identified as CVE-2021-20607 affects Mitsubishi Electric's GX Works2 software suite including GX Works2 versions 1.606G and prior, MELSOFT Navigator across all versions, and EZSocket across all versions. This vulnerability represents a critical security flaw that can be exploited to trigger denial of service conditions within industrial control systems. The vulnerability specifically manifests when these applications process maliciously crafted project files that contain manipulated integer values, creating conditions where arithmetic operations result in values that fall below the minimum representable range for the data type being used.
The technical flaw stems from inadequate input validation and boundary checking within the file parsing mechanisms of these industrial automation tools. When a user opens a specially crafted project file, the software attempts to perform arithmetic operations on integer variables that have been deliberately manipulated to cause underflow conditions. This occurs when the software subtracts a value from an integer that would result in a value smaller than the minimum allowed for that integer type, typically causing the application to crash or become unresponsive. The vulnerability is particularly concerning in industrial environments where these tools are used for programming and configuring programmable logic controllers and other critical control systems.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can severely disrupt industrial automation processes and manufacturing operations. In environments where GX Works2 is used for critical control system programming, an attacker could potentially cause production line shutdowns or system failures by convincing operators to open malicious project files. This type of attack could be particularly damaging in sectors such as automotive manufacturing, chemical processing, or power generation where industrial control systems require continuous operation. The vulnerability also represents a potential stepping stone for more sophisticated attacks, as it could be used to establish a foothold within industrial networks before attempting more targeted exploitation.
The vulnerability aligns with CWE-191, which specifically addresses integer underflow conditions, and represents a clear violation of secure coding practices that should be implemented in industrial software environments. From an attack perspective, this vulnerability maps to ATT&CK technique T1203, which involves the use of malicious files to gain initial access or cause system disruption. The attack vector relies on social engineering to convince users to open malicious files, making it particularly dangerous in environments where users may not be adequately trained in cybersecurity awareness. Organizations should consider implementing network segmentation to limit the potential impact of such attacks, along with regular security awareness training for personnel who handle industrial control system software. The recommended mitigations include immediate software updates from Mitsubishi Electric to address the integer underflow condition, implementation of strict file validation policies, and consideration of additional security controls such as application whitelisting to prevent execution of unauthorized software within industrial environments.