CVE-2017-13779 in Offline Utility Tool
Summary
by MITRE
GSTN_offline_tool in India Goods and Services Tax Network (GSTN) Offline Utility tool before 1.2 executes winstart-server.vbs from the "C:\GST Offline Tool" directory, which has insecure permissions. This allows local users to gain privileges by replacing winstart-server.vbs with arbitrary VBScript code. For example, a local user could create VBScript code for a TCP reverse shell, and use that later for Remote Command Execution.
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Analysis
by VulDB Data Team • 11/16/2019
The CVE-2017-13779 vulnerability resides within the India Goods and Services Tax Network's GSTN Offline Utility tool, specifically affecting versions prior to 1.2. This tool serves as a critical component for businesses to manage their tax-related data offline, making it an essential part of the country's tax administration infrastructure. The vulnerability stems from poor privilege management and insecure file permissions within the tool's installation directory at C:\GST Offline Tool. The winstart-server.vbs script, which is executed during the tool's operation, is located in a directory where local users possess write permissions, creating a fundamental security flaw that directly violates secure coding principles and privilege separation best practices.
The technical flaw represents a classic privilege escalation vulnerability where the system fails to properly enforce access controls on critical executable components. The winstart-server.vbs file operates with elevated privileges due to the tool's legitimate administrative requirements, yet the surrounding directory permissions allow any local user to modify or replace this script. This insecure permission model creates a direct attack vector where malicious actors can substitute the legitimate script with their own malicious VBScript code, effectively bypassing the normal execution flow of the application. The vulnerability aligns with CWE-276, which addresses improper file permissions, and demonstrates how weak access controls can lead to privilege escalation scenarios.
The operational impact of this vulnerability extends beyond simple local privilege escalation, as it enables attackers to achieve persistent remote command execution capabilities. A malicious local user could craft a VBScript payload that establishes a TCP reverse shell, effectively providing an attacker with a persistent backdoor into the system. This capability transforms a simple local privilege escalation into a potential full system compromise, as the attacker can execute arbitrary commands with the elevated privileges of the GSTN Offline Utility process. The vulnerability particularly concerns government infrastructure, as it could potentially allow attackers to access sensitive tax data, manipulate financial records, or disrupt critical tax administration functions. This type of attack vector is categorized under ATT&CK technique T1068, which covers local privilege escalation, and T1071, which addresses application layer protocol usage.
The remediation approach must address both the immediate permission issues and implement proper privilege management controls. Organizations should immediately update to version 1.2 or later of the GSTN Offline Utility, which resolves the insecure file permissions. System administrators must also implement proper access control lists on the installation directory, ensuring that only authorized users have write permissions to critical executable files. The principle of least privilege should be enforced, where the winstart-server.vbs script runs with minimal required permissions rather than elevated privileges. Additionally, regular security audits should verify that no other components within the GSTN ecosystem have similar permission misconfigurations, and that proper file integrity monitoring is implemented to detect unauthorized modifications to critical system files. This vulnerability serves as a prime example of how seemingly minor permission misconfigurations in government systems can create significant security risks that affect national infrastructure.