CVE-2018-9106 in AcySMS Extension
Summary
by MITRE
CSV Injection (aka Excel Macro Injection or Formula Injection) exists in the export feature in the Acyba AcySMS extension before 3.5.1 for Joomla! via a value that is mishandled in a CSV export.
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Analysis
by VulDB Data Team • 06/01/2025
The vulnerability CVE-2018-9106 represents a critical CSV injection flaw in the Acyba AcySMS extension for Joomla! versions prior to 3.5.1. This vulnerability falls under the category of insecure data handling and improper input validation, specifically affecting the CSV export functionality that processes user-supplied data. The flaw occurs when the extension fails to properly sanitize or escape data that contains potentially malicious formulas or commands, allowing attackers to inject executable content into exported CSV files. The vulnerability is particularly dangerous because it leverages the inherent behavior of spreadsheet applications like Microsoft Excel, which automatically interpret certain characters and patterns as formulas, creating a vector for arbitrary code execution.
The technical implementation of this vulnerability stems from the extension's failure to properly escape special characters in exported data, particularly those that are significant in spreadsheet formula syntax such as equals signs, plus signs, minus signs, and other operators that Excel interprets as formula indicators. When a user exports data containing these characters without proper sanitization, the resulting CSV file can contain formulas that execute when opened in spreadsheet applications. This behavior aligns with CWE-1236, which describes the weakness of not properly escaping special characters in data that is exported to formats interpreted by applications with formula execution capabilities. The vulnerability operates at the intersection of data export functionality and application interpretation behavior, making it particularly insidious as it can be triggered simply by opening a legitimate-looking CSV file in Excel or similar applications.
The operational impact of CVE-2018-9106 extends beyond simple data corruption or display issues, as it can lead to complete system compromise through various attack vectors. When an attacker crafts malicious input containing spreadsheet formulas, these can be designed to download and execute additional malware, steal credentials, or perform other malicious activities upon opening the CSV file. This vulnerability enables attackers to leverage the trust relationship between users and spreadsheet applications, making it particularly effective for social engineering attacks. The attack surface is broadened by the fact that many users regularly open CSV files from various sources without considering the potential security implications, and the vulnerability can be exploited through multiple attack paths including web application exploitation, phishing campaigns, and supply chain attacks. The weakness also relates to ATT&CK technique T1059.001, which covers command and scripting interpreter execution, as the injected formulas can execute system commands through the spreadsheet application's formula interpretation mechanisms.
Mitigation strategies for CVE-2018-9106 should focus on both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities. The primary recommendation is to upgrade to Acyba AcySMS version 3.5.1 or later, which includes proper input sanitization and escaping mechanisms for exported data. Organizations should implement comprehensive data sanitization practices that escape or quote special characters in export functionality, particularly those that have significance in spreadsheet applications. This includes implementing proper CSV escaping techniques such as prefixing formulas with a single quote or using proper CSV delimiters to prevent formula interpretation. Additionally, security teams should consider implementing content filtering and sandboxing mechanisms for CSV file processing, as well as user education programs to raise awareness about the risks of opening untrusted CSV files. Organizations should also consider implementing web application firewalls with rules specifically designed to detect and block suspicious CSV content patterns that could indicate injection attempts. The vulnerability highlights the importance of following secure coding practices and input validation standards, particularly when handling data that will be interpreted by multiple applications with different security models and execution contexts.