CVE-2021-20606 in GX Works2
Summary
by MITRE • 12/17/2021
Out-of-bounds Read 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 CVE-2021-20606 vulnerability represents a critical out-of-bounds read flaw affecting Mitsubishi Electric's GX Works2 software suite, specifically versions 1.606G and earlier, along with MELSOFT Navigator and EZSocket components across all versions. This vulnerability stems from insufficient input validation mechanisms within the software's project file parsing routines, where the application fails to properly validate array bounds when processing specially crafted project files. The flaw exists in the software's handling of malformed binary data structures that are part of the project file format, creating a scenario where memory access occurs beyond the allocated buffer boundaries. The vulnerability is particularly concerning as it can be exploited through social engineering techniques, requiring only that a user open a maliciously crafted project file, making it highly accessible to threat actors. This type of vulnerability falls under the CWE-125 Out-of-bounds Read classification, which is categorized as a fundamental memory safety issue that can lead to unpredictable behavior and system instability. The attack vector leverages the principle of privilege escalation through user interaction, as the exploitation requires user consent to open the malicious file, aligning with ATT&CK technique T1204.002 for User Execution via malicious file opening.
The technical implementation of this vulnerability demonstrates a classic buffer overrun scenario where the GX Works2 application attempts to read data beyond the allocated memory space when parsing project files. The software's parser does not perform adequate bounds checking on array indices or data structure lengths, allowing an attacker to craft project files containing malformed data sequences that trigger memory access violations. When the application encounters these specially constructed data elements, it attempts to read memory locations that fall outside the intended buffer boundaries, resulting in a segmentation fault or access violation that terminates the application process. This behavior constitutes a denial-of-service condition as defined by the vulnerability's impact description, effectively rendering the software unusable for legitimate operations. The vulnerability's exploitation does not require elevated privileges or complex attack chains, making it particularly dangerous in industrial control environments where software stability is paramount for operational continuity.
The operational impact of CVE-2021-20606 extends beyond simple service disruption to potentially compromise industrial automation systems that rely on Mitsubishi Electric's software ecosystem. In manufacturing and industrial control environments, the GX Works2 software serves as a critical tool for programming and configuring programmable logic controllers, making any DoS condition a significant threat to production continuity. The vulnerability's exploitation can lead to extended downtime during which operators cannot access or modify PLC configurations, potentially causing cascading failures in production processes. The attack's accessibility through simple file opening operations means that even untrained users could inadvertently trigger the vulnerability, making it a significant risk in environments with multiple users or shared workstations. Organizations using these software components face potential business disruption costs, including production delays, emergency support requirements, and the need for immediate software updates or patches. The vulnerability's presence in multiple software components within the Mitsubishi Electric ecosystem amplifies its impact, as organizations may need to coordinate patching efforts across several applications simultaneously.
Mitigation strategies for CVE-2021-20606 should prioritize immediate software updates from Mitsubishi Electric, as the vendor would have released patches addressing the specific buffer overflow conditions. Organizations should implement strict file validation policies, including the deployment of sandboxed environments for project file handling and the implementation of network segmentation to limit potential exploitation vectors. Security awareness training programs should be enhanced to educate users about the risks of opening untrusted project files, particularly in industrial environments where the attack surface may be expanded through shared network drives or file transfer protocols. Network monitoring solutions should be configured to detect unusual file access patterns or attempts to execute unknown project files. Additionally, organizations should consider implementing application whitelisting policies that restrict execution of unauthorized software versions, and establish robust backup procedures to ensure rapid recovery from potential exploitation incidents. The vulnerability highlights the importance of secure coding practices and input validation in industrial automation software, emphasizing the need for continuous security assessments of critical control system components. Regular vulnerability assessments and penetration testing should be conducted to identify similar memory safety issues within the industrial control system ecosystem, while incident response procedures should be updated to address potential DoS conditions affecting operational technology environments.