CVE-2018-7884 in Core Software Cleaner
Summary
by MITRE
An issue was discovered in DisplayLink Core Software Cleaner Application 8.2.1956. When the drivers are updated to a newer version, the product launches a process as SYSTEM to uninstall the old version: cl_1956.exe is run as SYSTEM on the %systemroot%\Temp folder, where any user can write a DLL (e.g., version.dll) to perform DLL Hijacking and elevate privileges to SYSTEM.
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Analysis
by VulDB Data Team • 02/15/2020
The vulnerability described in CVE-2018-7884 represents a critical privilege escalation flaw within the DisplayLink Core Software Cleaner Application version 8.2.1956. This issue arises from improper handling of executable processes during driver update operations, creating an exploitable condition that allows local attackers to elevate their privileges to the SYSTEM level. The vulnerability specifically manifests when the software attempts to uninstall older driver versions by launching cl_1956.exe with elevated privileges, creating a window of opportunity for malicious code injection.
The technical exploitation occurs through a well-known DLL hijacking attack vector where the malicious payload is placed in the %systemroot%\Temp directory, a location accessible to standard users. When the cl_1956.exe process executes with SYSTEM privileges, it searches for required DLL libraries in the specified directory order, loading any malicious DLL with the same name before the legitimate system libraries. This behavior directly violates security principles of least privilege and proper DLL resolution, as outlined in the CWE-426 weakness category which specifically addresses insecure library loading vulnerabilities. The vulnerability stems from the application's failure to properly specify library paths or validate the integrity of loaded modules during the uninstallation process.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete system control and access to all resources, files, and processes running under the SYSTEM context. This level of access enables attackers to modify system configurations, install persistent backdoors, extract sensitive data, or disable security mechanisms. The vulnerability is particularly concerning because it requires no special privileges to exploit, making it accessible to any local user who can write to the Temp directory. This characteristic aligns with ATT&CK technique T1068 which covers 'Exploitation for Privilege Escalation' and specifically addresses the use of insecure library loading as a method for elevation.
Mitigation strategies for this vulnerability should focus on immediate remediation through software updates from DisplayLink, as the vendor has likely released patches addressing this specific issue. System administrators should implement additional controls such as restricting write permissions to the %systemroot%\Temp directory for non-privileged users, implementing application whitelisting policies to prevent execution of unauthorized binaries, and conducting regular security audits of installed software for similar privilege escalation vulnerabilities. The vulnerability also highlights the importance of proper process elevation controls and secure coding practices that ensure executables launched with elevated privileges do not load libraries from insecure locations, as recommended in the OWASP Secure Coding Practices and Microsoft's Secure Application Lifecycle guidelines.