CVE-2021-1366 in AnyConnect Secure Mobility Client
Summary
by MITRE • 02/17/2021
A vulnerability in the interprocess communication (IPC) channel of Cisco AnyConnect Secure Mobility Client for Windows could allow an authenticated, local attacker to perform a DLL hijacking attack on an affected device if the VPN Posture (HostScan) Module is installed on the AnyConnect client. This vulnerability is due to insufficient validation of resources that are loaded by the application at run time. An attacker could exploit this vulnerability by sending a crafted IPC message to the AnyConnect process. A successful exploit could allow the attacker to execute arbitrary code on the affected machine with SYSTEM privileges. To exploit this vulnerability, the attacker needs valid credentials on the Windows system.
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Analysis
by VulDB Data Team • 03/02/2021
The vulnerability identified as CVE-2021-1366 represents a critical security flaw within Cisco AnyConnect Secure Mobility Client for Windows operating systems. This vulnerability specifically targets the interprocess communication channel mechanism that facilitates communication between different components of the VPN client application. The affected system components include the VPN Posture (HostScan) Module which is installed as part of the AnyConnect client package, creating a potential attack surface that malicious actors can exploit to gain unauthorized access to systems. The vulnerability exists within the application's runtime resource loading mechanism, where insufficient validation occurs during the loading of dynamic link libraries that are critical for proper application functionality.
The technical exploitation of this vulnerability requires an authenticated local attacker who possesses valid Windows system credentials, making it a privilege escalation issue rather than a remote attack vector. Attackers can leverage this weakness by crafting and sending malicious IPC messages directly to the AnyConnect process, which then loads the malicious dynamic link library without proper validation checks. This process allows the attacker to execute arbitrary code with SYSTEM privileges, effectively providing complete control over the compromised system. The flaw stems from the application's failure to properly validate and sanitize the resources loaded at runtime, creating an environment where attacker-controlled DLL files can be executed without proper authorization or integrity checks. This type of vulnerability aligns with the Common Weakness Enumeration category CWE-427, which describes uncontrolled search path elements that can lead to insecure library loading practices.
The operational impact of CVE-2021-1366 is severe and far-reaching within enterprise environments that utilize Cisco AnyConnect for remote access solutions. Organizations with multiple users accessing corporate networks through AnyConnect clients face significant risk of compromise when this vulnerability exists in their infrastructure. The ability to execute code with SYSTEM privileges means that attackers can bypass standard user account restrictions, access sensitive data, modify system configurations, and potentially establish persistent backdoors within the network. This vulnerability particularly affects organizations that have deployed the VPN Posture (HostScan) Module, as this component is specifically mentioned as being vulnerable to the attack vector. The attack requires local system access and valid credentials, which means that while it may be more difficult to exploit than remote attacks, it can still be leveraged by insider threats or attackers who have already gained initial access to the system through other means.
Mitigation strategies for CVE-2021-1366 should prioritize immediate patching of affected Cisco AnyConnect client installations through official security updates provided by Cisco. Organizations should also implement network monitoring to detect unusual IPC communication patterns that might indicate exploitation attempts, as this vulnerability relies on specific interprocess communication mechanisms. System administrators should consider disabling or removing the VPN Posture (HostScan) Module if it is not essential for their security posture, as this component is specifically identified as vulnerable. Additionally, implementing least privilege principles and ensuring that user accounts have minimal necessary permissions can help reduce the potential impact of successful exploitation. The vulnerability demonstrates the importance of secure coding practices and proper resource validation in application development, particularly for applications that handle sensitive network communications and require elevated privileges for operation. Organizations should also consider implementing application whitelisting policies to prevent unauthorized DLL loading and enhance overall system security posture against similar vulnerabilities.