CVE-2011-2041 in AnyConnect Secure Mobility Client
Summary
by MITRE
The Start Before Logon (SBL) functionality in Cisco AnyConnect Secure Mobility Client (formerly AnyConnect VPN Client) before 2.3.254 on Windows, and on Windows Mobile, allows local users to gain privileges via unspecified user-interface interaction, aka Bug ID CSCta40556.
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Analysis
by VulDB Data Team • 11/08/2021
The vulnerability identified as CVE-2011-2041 resides within the Start Before Logon (SBL) functionality of Cisco AnyConnect Secure Mobility Client, a widely deployed VPN solution for enterprise and government networks. This security flaw affects versions prior to 2.3.254 on both standard Windows platforms and Windows Mobile devices, creating a critical privilege escalation vector that could be exploited by local attackers. The vulnerability specifically leverages unspecified user-interface interaction mechanisms to enable unauthorized privilege elevation, making it particularly concerning given the widespread adoption of AnyConnect across critical infrastructure environments. The bug ID CSCta40556 further identifies this as a significant security concern within Cisco's product portfolio.
The technical implementation of this vulnerability stems from improper privilege handling within the SBL feature, which is designed to allow applications to start automatically before a user logs into the system. This functionality is commonly used to ensure network connectivity remains available during system boot processes or user logon sequences. However, the flaw in the AnyConnect client implementation allows local users to manipulate the user interface elements in such a way that they can escalate their privileges to system-level access. The vulnerability essentially represents a failure in access control enforcement within the client's startup mechanisms, where the system does not properly validate the privileges of entities attempting to interact with the SBL functionality. This weakness aligns with CWE-284, which addresses improper access control issues, and specifically manifests as an improper privilege management scenario.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the security model of systems running vulnerable AnyConnect clients. Attackers who can execute local code on a target system can leverage this vulnerability to gain system-level privileges, potentially enabling them to install malicious software, modify system configurations, access sensitive data, or establish persistent backdoors. The SBL functionality's design intent was to provide seamless connectivity during system startup, but this feature becomes a security liability when local privilege escalation is possible. Organizations using vulnerable AnyConnect versions face significant risk, particularly in environments where physical security controls are insufficient or where users might be tricked into performing specific user interface interactions. The vulnerability's exploitation requires local access but can result in complete system compromise, making it a particularly attractive target for attackers seeking persistent access to networked systems.
Mitigation strategies for this vulnerability require immediate patching of affected AnyConnect clients to version 2.3.254 or later, which contains the necessary security fixes. Organizations should also implement comprehensive vulnerability management processes to ensure all instances of the AnyConnect client across their network are updated promptly. System administrators should consider disabling the Start Before Logon functionality where it is not strictly required, as this can reduce the attack surface for this particular vulnerability. Network monitoring should be enhanced to detect unusual privilege escalation activities, and security teams should conduct thorough audits of systems running vulnerable AnyConnect versions. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the use of legitimate system tools and features to gain elevated privileges. Additionally, implementing least privilege principles and regular security assessments can help reduce the potential impact of similar vulnerabilities in the future, as outlined in the NIST Cybersecurity Framework guidelines for managing software vulnerabilities effectively.