CVE-2015-0761 in AnyConnect Secure Mobility Client
Summary
by MITRE
Cisco AnyConnect Secure Mobility Client before 3.1(8009) and 4.x before 4.0(2052) on Linux does not properly implement unspecified internal functions, which allows local users to obtain root privileges via crafted vpnagent options, aka Bug ID CSCus86790.
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Analysis
by VulDB Data Team • 07/01/2017
The vulnerability described in CVE-2015-0761 represents a critical privilege escalation flaw within Cisco AnyConnect Secure Mobility Client versions prior to 3.1(8009) and 4.x before 4.0(2052) on Linux systems. This issue stems from improper implementation of unspecified internal functions within the vpnagent component, which serves as a critical subsystem for managing VPN connections and system integration. The vulnerability specifically affects the Linux implementation of the AnyConnect client, which is widely deployed for remote access and secure network connectivity in enterprise environments. The flaw manifests when local users can manipulate vpnagent options in ways that bypass normal security controls, ultimately enabling them to escalate their privileges to the root level.
The technical mechanism behind this vulnerability involves the improper handling of internal function calls within the vpnagent daemon process. When the AnyConnect client initializes or manages VPN connections, it relies on vpnagent to perform various system-level operations including network configuration, authentication handling, and privilege management. The unspecified internal functions that fail to be properly implemented contain logic that should validate user inputs and enforce proper privilege boundaries. However, due to incomplete implementation, these functions accept crafted options that can be manipulated to trigger unintended behavior within the system. This misimplementation creates a path where local attackers can inject malicious parameters that cause the vpnagent process to execute with elevated privileges, effectively bypassing the normal user-to-root privilege escalation restrictions.
The operational impact of this vulnerability is severe and far-reaching for organizations relying on Cisco AnyConnect for remote access security. A local attacker who gains access to a system running the vulnerable AnyConnect client can exploit this flaw to gain root access without requiring additional authentication or authorization. This privilege escalation capability transforms a local access point into a complete system compromise, potentially allowing attackers to install malware, exfiltrate sensitive data, modify system configurations, or establish persistent backdoors. The vulnerability is particularly dangerous because it requires no network access or specialized knowledge beyond local system access, making it an attractive target for both insider threats and attackers who have already gained initial foothold within a network. Organizations using AnyConnect for remote work or branch office connectivity face significant risk as this vulnerability can be exploited by anyone with legitimate local access to a system.
The vulnerability aligns with CWE-264, which covers "Permissions, Privileges, and Access Controls" and specifically addresses improper privilege management in software implementations. From an ATT&CK framework perspective, this vulnerability maps to T1068, "Exploitation for Privilege Escalation," and potentially T1548.001, "Abuse of sudo", as the flaw allows local users to escalate privileges through improper function implementation rather than traditional privilege escalation vectors. Organizations should prioritize immediate remediation by upgrading to Cisco AnyConnect versions 3.1(8009) or 4.0(2052) and later, which contain the necessary patches to address the unspecified internal function implementation issues. Additionally, system administrators should implement monitoring for unauthorized vpnagent process modifications and consider restricting local user access to systems running vulnerable AnyConnect clients. The patching process should include thorough testing in production environments to ensure that the updated client maintains proper functionality for legitimate remote access operations while eliminating the privilege escalation vector.