CVE-2020-5145 in Global VPN Client
Summary
by MITRE • 10/28/2020
SonicWall Global VPN client version 4.10.4.0314 and earlier have an insecure library loading (DLL hijacking) vulnerability. Successful exploitation could lead to remote code execution in the target system.
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Analysis
by VulDB Data Team • 11/29/2020
The SonicWall Global VPN client vulnerability identified as CVE-2020-5145 represents a critical insecure library loading flaw that affects versions 4.10.4.0314 and earlier. This vulnerability resides in the client-side application's dynamic link library (DLL) loading mechanism, which fails to properly validate or authenticate the source of dynamically loaded libraries. The flaw allows attackers to place malicious DLL files in directories that are searched by the application during runtime, enabling unauthorized code execution with the privileges of the victim user. This type of vulnerability is classified under CWE-427 Uncontrolled Search Path Element, which specifically addresses insecure library loading practices where the application searches for libraries in predictable locations without proper validation. The vulnerability demonstrates a classic path traversal and privilege escalation vector that can be exploited in networked environments where the VPN client is installed.
The technical exploitation of this vulnerability requires an attacker to position a malicious DLL file in a location that will be searched by the SonicWall client application during its execution cycle. When the application attempts to load a required library, it will inadvertently load the attacker-controlled DLL instead of the legitimate one, leading to arbitrary code execution. The attack can be executed remotely through network-based delivery mechanisms, making it particularly dangerous in enterprise environments where multiple users may be running vulnerable versions of the client. The vulnerability's impact is amplified by the fact that the VPN client typically runs with elevated privileges, potentially allowing attackers to achieve system-level compromise. This aligns with ATT&CK technique T1059 Command and Scripting Interpreter, as the execution of malicious code through DLL hijacking enables attackers to run arbitrary commands on the compromised system.
The operational impact of CVE-2020-5145 extends beyond simple remote code execution to encompass potential full system compromise and lateral movement capabilities within affected networks. Organizations using SonicWall VPN clients in their infrastructure face significant risk, particularly in environments where the client is deployed across multiple endpoints without proper security controls. The vulnerability can be exploited by attackers who gain access to the network through other means, such as phishing campaigns or initial access vectors, and then leverage the vulnerable client to escalate privileges and maintain persistent access. Network segmentation and proper application whitelisting could provide partial protection, but the fundamental flaw in the library loading mechanism remains a critical weakness that requires immediate remediation. This vulnerability demonstrates the importance of proper secure coding practices and the dangers of insecure library loading in enterprise applications, particularly those handling network security functions. Organizations should implement immediate patching strategies and consider network monitoring to detect potential exploitation attempts.
Mitigation strategies for CVE-2020-5145 should prioritize immediate patch deployment from SonicWall, as version 4.10.4.0314 and later contain fixes for this vulnerability. System administrators should conduct comprehensive inventory checks to identify all affected client installations and implement mandatory update policies. Additional protective measures include implementing application control solutions such as Windows AppLocker or similar technologies to restrict which DLLs can be loaded by the VPN client. Network administrators should monitor for unusual DLL loading patterns and implement endpoint detection and response capabilities to identify potential exploitation attempts. The vulnerability also highlights the need for secure coding practices and regular security assessments of network infrastructure applications, particularly those handling privileged operations. Organizations should consider implementing least privilege principles for VPN client installations and ensure that the client application runs with minimal required permissions. This vulnerability serves as a reminder of the critical importance of maintaining up-to-date security patches and implementing robust application security controls to prevent exploitation of insecure library loading mechanisms.