CVE-2021-38424 in DIALink
Summary
by MITRE • 11/04/2021
The tag interface of Delta Electronics DIALink versions 1.2.4.0 and prior is vulnerable to an attacker injecting formulas into the tag data. Those formulas may then be executed when it is opened with a spreadsheet application.
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Analysis
by VulDB Data Team • 11/09/2021
The vulnerability identified as CVE-2021-38424 affects Delta Electronics DIALink software versions 1.2.4.0 and earlier, presenting a significant security risk through improper input validation within the tag interface functionality. This flaw enables attackers to inject malicious formulas into tag data that can subsequently execute when the data is opened in spreadsheet applications such as Microsoft Excel or Google Sheets. The vulnerability stems from insufficient sanitization of user-supplied data within the tag handling mechanism, creating an environment where crafted input can be interpreted as executable code rather than mere data.
The technical implementation of this vulnerability involves the manipulation of tag data structures that are designed to store configuration parameters and operational metrics for industrial automation systems. When these tags contain specially crafted formula strings beginning with characters like equals signs or other spreadsheet function indicators, the vulnerable software fails to properly escape or validate these inputs before storing them. This oversight creates a path for formula injection attacks that can leverage the spreadsheet application's built-in functionality to execute arbitrary code or perform unauthorized operations. The attack vector specifically targets the data processing pipeline where tag information flows from the DIALink interface into spreadsheet-compatible formats, making the vulnerability particularly dangerous in industrial control environments where such data exchange is common.
The operational impact of this vulnerability extends beyond simple data corruption, as it can enable attackers to gain unauthorized access to industrial systems through a technique known as spreadsheet-based command execution. When an unsuspecting user opens a compromised tag file in a spreadsheet application, the injected formulas can trigger various malicious behaviors including data exfiltration, system command execution, or even payload delivery mechanisms. This represents a sophisticated attack pattern that combines elements of social engineering with software exploitation, as the attack requires user interaction but leverages the trust relationship between the industrial application and spreadsheet software. The vulnerability directly relates to CWE-15 (Improper Neutralization of Special Elements) and CWE-74 (Improper Neutralization of Special Elements in Output), which classify the issue as a failure to properly sanitize data before processing. From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1059.005 (Command and Scripting Interpreter: Visual Basic) and T1204.002 (User Execution: Malicious File), demonstrating how industrial control systems can become entry points for broader network compromise.
Organizations utilizing Delta Electronics DIALink software must implement immediate mitigations to address this vulnerability, including upgrading to versions 1.2.5.0 or later where the issue has been resolved through proper input validation and sanitization mechanisms. System administrators should also establish network segmentation policies to limit access to industrial control systems and implement strict file validation procedures for any tag data imported into spreadsheet applications. Additionally, user education programs should emphasize the importance of verifying file sources and avoiding opening untrusted tag files in spreadsheet applications. The vulnerability highlights the critical need for security-by-design principles in industrial automation software, particularly in environments where multiple software systems interact and exchange data. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain comprehensive monitoring of industrial network traffic for potential exploitation attempts.