CVE-2018-6384 in NSClient++
Summary
by MITRE
Unquoted Windows search path vulnerability in NSClient++ before 0.4.1.73 allows non-privileged local users to execute arbitrary code with elevated privileges on the system via a malicious program.exe executable in the %SYSTEMDRIVE% folder.
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Analysis
by VulDB Data Team • 12/31/2019
The vulnerability identified as CVE-2018-6384 represents a critical unquoted search path issue within NSClient++ versions prior to 0.4.1.73, which operates as a monitoring agent for windows systems. This flaw stems from the improper handling of executable paths during the system search process, creating a privilege escalation vector that can be exploited by non-privileged local users. The vulnerability specifically affects the way the application resolves executable paths when searching for required binaries, allowing attackers to place malicious executables in locations that are searched before the intended targets.
The technical implementation of this vulnerability occurs when NSClient++ attempts to locate and execute programs without properly quoting the search paths in its configuration. This behavior aligns with CWE-428, which addresses the improper resolution of a search path, and specifically relates to CWE-78, which covers improper neutralization of special elements used in OS commands. When the system searches for executables, it follows a specific order that includes the %SYSTEMDRIVE% directory, and if this path is not properly quoted in the application's configuration, it becomes a potential attack surface. The flaw allows an attacker to place a malicious program.exe file in the root of the system drive, where the application will execute it with elevated privileges due to the system's search order.
The operational impact of this vulnerability is severe as it enables local privilege escalation from standard user accounts to SYSTEM level privileges without requiring any special authentication or network access. The exploitability is straightforward since the attacker only needs to place a malicious executable in the %SYSTEMDRIVE% directory, which is typically writable by standard users and is part of the default Windows search path. This vulnerability can be leveraged by attackers to establish persistent backdoors, escalate privileges for further exploitation, or execute arbitrary code with full system access. The attack chain typically involves placing a malicious binary in the system drive root, which then gets executed by NSClient++ with elevated privileges, potentially allowing the attacker to gain complete control over the system.
Mitigation strategies for CVE-2018-6384 primarily involve updating NSClient++ to version 0.4.1.73 or later, which addresses the unquoted search path issue through proper path quoting in the application's configuration handling. Security administrators should also implement the principle of least privilege by restricting write access to system drives and monitoring for unauthorized executable placements. Additionally, the use of application whitelisting solutions such as Windows Defender Application Control or similar technologies can prevent execution of unauthorized binaries even if the vulnerability exists. From an ATT&CK framework perspective, this vulnerability maps to T1068, which covers the use of elevated privileges for privilege escalation, and T1059, which covers execution through command and scripting interpreters. Organizations should also consider implementing security controls such as regular vulnerability assessments, patch management processes, and monitoring for suspicious file creation patterns in system directories to detect potential exploitation attempts.