Cisco AnyConnect Secure Mobility Client for Windows DLL Hijacking Local Privilege Escalation (CVE-2020-3433)

1. Vulnerability Overview & Root Cause

A vulnerability in the interprocess communication (IPC) channel of Cisco AnyConnect Secure Mobility Client for Windows allows an authenticated, local attacker to perform a DLL hijacking attack (CWE-427). The AnyConnect service runs with high privileges (SYSTEM) to manage network configurations. The root cause of this vulnerability is the insufficient validation of resources and DLL paths loaded by the application at runtime via the IPC channel. This lack of validation allows an attacker to force the high-privilege process to load arbitrary libraries.

2. Exploitation Mechanics & Attack Scenario

To exploit this vulnerability, an attacker must first obtain valid local credentials on the target Windows system. The attacker then sends a crafted IPC message to the active AnyConnect background process. This message instructs the service to load a specific DLL from a directory where the attacker has write permissions. Because the AnyConnect service fails to verify the signature or integrity of the DLL before loading it, the malicious payload is executed within the security context of the SYSTEM account, achieving Local Privilege Escalation (LPE).

3. Infrastructure & Business Impact

This vulnerability is cataloged in CISA's Known Exploited Vulnerabilities (KEV), indicating active exploitation in the wild. While it requires local access to exploit, it is highly valuable to threat actors as a secondary stage of attack. Once initial access is gained via phishing or other means, attackers leverage this vulnerability to bypass endpoint security controls, dump credentials, and deploy ransomware across the enterprise network by gaining full SYSTEM control.