CVE-2016-4901 in e-Tax
Summary
by MITRE
Untrusted search path vulnerability in The installer of e-Tax Software all versions allows remote attackers to gain privileges via a Trojan horse DLL in an unspecified directory.
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Analysis
by VulDB Data Team • 10/01/2020
The CVE-2016-4901 vulnerability represents a critical untrusted search path issue within the e-Tax Software installer across all affected versions. This weakness stems from the installer's improper handling of dynamic link library (dll) loading mechanisms, where the software fails to validate or restrict the directories from which it loads executable components. The vulnerability creates a path traversal risk that allows malicious actors to place a specially crafted Trojan horse dll file in an unspecified directory that the installer will subsequently load and execute with elevated privileges. This flaw directly aligns with CWE-426, which categorizes untrusted search path vulnerabilities as a serious security concern that can lead to privilege escalation and arbitrary code execution.
The technical exploitation of this vulnerability occurs when an attacker places a malicious dll file in a directory that appears earlier in the system's search path than the legitimate software components. During the installation process, the e-Tax installer performs a recursive search through predefined directories without proper validation of file sources or integrity checks. When the installer encounters the malicious dll file, it loads and executes the code with the privileges of the installer process, which typically runs with administrative rights. This privilege escalation vector can enable attackers to install additional malware, modify system configurations, or establish persistence mechanisms within the target environment. The vulnerability operates under the principle of DLL hijacking as described in the ATT&CK framework under technique T1574.001, where adversaries manipulate the dynamic link library loading process to execute malicious code.
The operational impact of CVE-2016-4901 extends beyond simple privilege escalation to encompass broader system compromise and data theft capabilities. Organizations using the affected e-Tax software become vulnerable to sophisticated attack campaigns where adversaries can leverage this weakness to establish persistent access, exfiltrate sensitive tax-related information, or deploy additional malicious payloads. The vulnerability's remote exploitation capability means that attackers can potentially compromise systems without physical access, making it particularly dangerous for organizations that rely on remote desktop connections or network-based installation processes. The installer-based nature of the vulnerability means that even systems that have not yet installed the software can be compromised if an attacker can influence the installation environment, creating a window of opportunity for exploitation before legitimate installation occurs. This makes the vulnerability particularly concerning for enterprise environments where software deployment processes may not strictly control installation directories or where users may inadvertently execute malicious installers.
Mitigation strategies for CVE-2016-4901 should focus on implementing strict directory access controls and proper dll loading mechanisms within the e-Tax software installation process. Organizations should ensure that the installer operates with minimal required privileges and that all dll loading operations include source validation and integrity checks. System administrators should implement application whitelisting policies that restrict which dll files can be loaded from specific directories, particularly those that appear in the default search path. The recommended approach includes configuring the Windows search path to prioritize system directories over user-controlled locations and implementing proper file system permissions that prevent unauthorized dll placement. Additionally, organizations should consider deploying endpoint protection solutions that monitor for suspicious dll loading activities and implement regular security assessments to identify and remediate similar untrusted search path vulnerabilities in other software components. The mitigation efforts should align with security best practices outlined in NIST SP 800-128 and other federal cybersecurity guidelines for software development and deployment security.