CVE-2018-16189 in UNLHA32.DLL
Summary
by MITRE
Untrusted search path vulnerability in Self-Extracting Archives created by UNLHA32.DLL prior to Ver 3.00 allows an attacker to gain privileges via a Trojan horse DLL in an unspecified directory.
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Analysis
by VulDB Data Team • 05/10/2020
The vulnerability identified as CVE-2018-16189 represents a critical untrusted search path issue within the UNLHA32.DLL library component used in self-extracting archive functionality. This flaw exists in versions prior to 3.00 and creates a significant security risk through improper DLL loading mechanisms that do not validate the source or authenticity of loaded modules. The vulnerability stems from the library's failure to implement proper security controls when searching for required dynamic link libraries during the extraction process, creating an opportunity for malicious actors to execute arbitrary code with elevated privileges.
The technical implementation of this vulnerability involves the insecure loading of DLL modules from directories that are not properly validated or secured. When a self-extracting archive is executed, the UNLHA32.DLL component searches for required libraries in a predetermined search path that includes user-writable directories without proper access controls. This behavior directly aligns with CWE-427, which describes uncontrolled search path dependencies, and CWE-428, which addresses untrusted search path vulnerabilities. The attack vector occurs when an attacker places a malicious Trojan horse DLL in one of the directories that the vulnerable library searches, causing the system to load and execute the malicious code instead of the legitimate library component.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system compromise and persistent backdoor access. An attacker who successfully exploits this vulnerability can execute code with the privileges of the user running the self-extracting archive, potentially leading to full system compromise if the archive is executed with elevated permissions. The vulnerability is particularly dangerous because it can be exploited through social engineering tactics where users unknowingly execute malicious archives, or through automated delivery methods that place the malicious DLL in the search path. This type of attack pattern corresponds to ATT&CK technique T1059.001 for command and script interpreter and T1068 for exploit for privilege escalation.
Mitigation strategies for this vulnerability require immediate remediation through updating to UNLHA32.DLL version 3.00 or later, which implements proper DLL loading security measures. System administrators should also implement additional controls such as restricting write permissions to directories in the system search path, implementing application whitelisting policies, and monitoring for suspicious DLL loading activities. The implementation of secure coding practices including explicit path resolution and DLL verification mechanisms would prevent similar vulnerabilities from occurring in future implementations. Organizations should conduct thorough vulnerability assessments to identify systems running vulnerable versions and ensure proper patch management procedures are in place to prevent exploitation of this and similar search path vulnerabilities that could lead to complete system compromise.