CVE-2020-3435 in AnyConnect Secure Mobility Client
Summary
by MITRE
A vulnerability in the interprocess communication (IPC) channel of Cisco AnyConnect Secure Mobility Client for Windows could allow an authenticated, local attacker to overwrite VPN profiles on an affected device. To exploit this vulnerability, the attacker would need to have valid credentials on the Windows system. The vulnerability is due to insufficient validation of user-supplied input. An attacker could exploit this vulnerability by sending a crafted IPC message to the AnyConnect process on an affected device. A successful exploit could allow the attacker to modify VPN profile files. To exploit this vulnerability, the attacker would need to have valid credentials on the Windows system.
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Analysis
by VulDB Data Team • 11/10/2020
The vulnerability identified as CVE-2020-3435 resides within the interprocess communication mechanisms of Cisco AnyConnect Secure Mobility Client for Windows operating systems. This security flaw represents a critical weakness in the client's architecture that could be exploited by malicious actors with local system access. The vulnerability specifically affects the IPC channel that facilitates communication between different processes within the AnyConnect application, creating an attack surface that adversaries can leverage to manipulate VPN configuration data. The issue stems from inadequate input validation procedures that fail to properly sanitize or verify the legitimacy of data received through the IPC channel, allowing potentially malicious payloads to be processed without proper authorization checks.
The technical exploitation of this vulnerability requires an authenticated local attacker who possesses valid Windows system credentials, which significantly reduces the attack surface but does not eliminate the risk entirely. Attackers can craft specialized IPC messages designed to target the AnyConnect process and manipulate VPN profile files stored on the affected device. This flaw operates at the system level where the IPC channel lacks proper validation mechanisms to distinguish between legitimate and malicious communication attempts. The insufficient input validation creates a pathway for privilege escalation through data manipulation, as the attacker can effectively overwrite existing VPN configurations with maliciously crafted profile data. This represents a classic example of a buffer over-read or improper input validation vulnerability that falls under the CWE-20 category of "Improper Input Validation" and could potentially be leveraged for privilege escalation or persistence mechanisms.
The operational impact of this vulnerability extends beyond simple profile modification, as compromised VPN configurations could lead to unauthorized network access, data exfiltration, or disruption of legitimate network communications. Attackers could potentially modify VPN profiles to redirect traffic through malicious endpoints, create backdoor access points, or disable security features within the AnyConnect client. This vulnerability directly impacts the integrity of the VPN connection management system and could compromise the confidentiality and availability of network resources. The attack vector operates through the Windows IPC mechanisms, making it particularly dangerous in enterprise environments where VPN clients are widely deployed and often used for accessing sensitive corporate resources. Organizations using Cisco AnyConnect clients are at risk of persistent threats that could maintain access to their networks through manipulated VPN profiles.
Mitigation strategies for CVE-2020-3435 should focus on implementing comprehensive access controls and privilege management within the Windows environment. System administrators should enforce strict credential policies and ensure that only authorized personnel have local access to systems running AnyConnect clients. Regular security updates and patches from Cisco should be deployed immediately upon availability, as this vulnerability was addressed through software updates that enhanced input validation in the IPC channel. Network segmentation and monitoring of IPC communications can help detect anomalous behavior that might indicate exploitation attempts. The implementation of principle of least privilege should be enforced, limiting local user access to systems containing VPN client configurations. Additionally, organizations should conduct regular security assessments of their VPN infrastructure and implement monitoring solutions that can detect unauthorized modifications to VPN profile files. This vulnerability demonstrates the importance of secure coding practices and proper input validation in system components that handle interprocess communications, aligning with ATT&CK technique T1059.007 for process injection and T1566 for credential access through local system exploitation.