CVE-2015-4173 in SonicWALL NetExtender
Summary
by MITRE
Unquoted Windows search path vulnerability in the autorun value in Dell SonicWall NetExtender with firmware before 7.5.1.2 and 8.x before 8.0.0.3 allows local users to gain privileges via a Trojan horse program in the %SYSTEMDRIVE% folder.
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Analysis
by VulDB Data Team • 06/13/2022
The vulnerability CVE-2015-4173 represents a critical unquoted search path issue affecting Dell SonicWall NetExtender firmware versions prior to 7.5.1.2 and 8.x versions before 8.0.0.3. This flaw resides within the autorun functionality of the NetExtender client software, specifically in how the system handles executable paths during the autorun process. The vulnerability stems from the Windows operating system's search path resolution mechanism where the system does not properly quote paths when searching for executables, creating opportunities for privilege escalation attacks.
The technical implementation of this vulnerability exploits the Windows search path behavior where the operating system searches for executables in a specific order without requiring explicit path quoting. When the NetExtender client processes autorun values that contain unquoted paths, the system will traverse directories in sequence until it finds an executable matching the specified name. This creates a scenario where a malicious actor can place a Trojan horse program in the %SYSTEMDRIVE% folder, which is typically the first location in the search path, allowing the malicious executable to be executed with elevated privileges.
From a cybersecurity perspective, this vulnerability aligns with CWE-428, which describes the weakness of unquoted search paths, and maps to ATT&CK technique T1068, which covers privilege escalation through local exploitation. The operational impact of this vulnerability is significant as it allows local users to achieve privilege escalation without requiring remote access or complex attack vectors. The attack requires only that a malicious program be placed in the %SYSTEMDRIVE% folder, which is typically writable by local users, making the exploitation relatively straightforward and persistent.
The attack vector leverages the inherent trust model of Windows autorun functionality where system components automatically execute programs based on registry entries without proper path validation. This vulnerability affects the NetExtender client's handling of autorun values in a way that bypasses normal security controls, enabling malicious code execution with system-level privileges. The risk is compounded by the fact that many users may not be aware of the specific registry entries being modified by the NetExtender client, making detection and remediation more challenging.
Organizations should implement immediate mitigations including updating to firmware versions 7.5.1.2 or 8.0.0.3 where the vulnerability has been patched, applying the principle of least privilege to reduce the impact of potential exploitation, and conducting thorough security audits of autorun configurations. Additionally, system administrators should monitor for unauthorized modifications to registry entries related to autorun functionality and implement proper path quoting practices in all system configurations to prevent similar vulnerabilities from being introduced in other applications or system components.