CVE-2018-0247 in Wireless LAN Controller
Summary
by MITRE
A vulnerability in Web Authentication (WebAuth) clients for the Cisco Wireless LAN Controller (WLC) and Aironet Access Points running Cisco IOS Software could allow an unauthenticated, adjacent attacker to bypass authentication and pass traffic. The vulnerability is due to incorrect implementation of authentication for WebAuth clients in a specific configuration. An attacker could exploit this vulnerability by sending traffic to local network resources without having gone through authentication. A successful exploit could allow the attacker to bypass authentication and pass traffic. This affects Cisco Aironet Access Points running Cisco IOS Software and Cisco Wireless LAN Controller (WLC) releases prior to 8.5.110.0 for the following specific WLC configuration only: (1) The Access Point (AP) is configured in FlexConnect Mode with NAT. (2) The WLAN is configured for central switching, meaning the client is being assigned a unique IP address. (3) The AP is configured with a Split Tunnel access control list (ACL) for access to local network resources, meaning the AP is doing the NAT on the connection. (4) The client is using WebAuth. This vulnerability does not apply to .1x clients in the same configuration. Cisco Bug IDs: CSCvc79502, CSCvf71789.
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Analysis
by VulDB Data Team • 03/08/2023
The vulnerability described in CVE-2018-0247 represents a critical authentication bypass flaw within Cisco's wireless networking infrastructure, specifically affecting Web Authentication clients operating on Cisco Wireless LAN Controllers and Aironet Access Points. This security weakness stems from improper implementation of authentication mechanisms within a specific network configuration scenario that combines multiple operational parameters to create an exploitable condition. The flaw manifests when wireless clients attempt to access network resources through the WebAuth authentication process, allowing unauthorized access to local network resources without proper authentication. The vulnerability is particularly concerning because it targets adjacent attackers who can leverage the flaw from within the local network perimeter, eliminating the need for complex remote exploitation techniques.
The technical implementation of this vulnerability is rooted in the specific combination of configuration parameters that must be present for the flaw to manifest. The affected systems require the Access Point to operate in FlexConnect Mode with Network Address Translation enabled, while the WLAN must be configured for central switching to assign unique IP addresses to clients. Additionally, the AP must be configured with a Split Tunnel access control list that performs NAT on connections, creating a scenario where the authentication bypass occurs during the traffic forwarding process. The vulnerability specifically targets WebAuth clients while excluding 802.1x clients from the same configuration, indicating that the flaw is particular to the Web Authentication implementation rather than a fundamental issue with the entire wireless authentication framework. This selective impact suggests that the vulnerability exists within the WebAuth client processing logic rather than at the network protocol level, making it a software implementation flaw rather than a protocol-level weakness.
The operational impact of this vulnerability extends beyond simple unauthorized network access, creating a potential pathway for attackers to establish persistent network presence and escalate privileges within the local network environment. An attacker exploiting this vulnerability can bypass authentication mechanisms entirely, allowing them to pass traffic directly to local network resources without proper authorization, potentially gaining access to sensitive internal systems, servers, or data repositories. The attack vector requires only adjacent network access, meaning that an attacker positioned within the same network segment can exploit the vulnerability without requiring sophisticated network reconnaissance or complex attack chains. This characteristic significantly lowers the barrier to exploitation and increases the potential for successful attacks within corporate or institutional environments where wireless networks are extensively deployed. The vulnerability's impact is particularly severe in environments where wireless networks provide access to critical infrastructure, as it could enable attackers to bypass network security controls and gain unauthorized access to sensitive resources.
Mitigation strategies for this vulnerability must focus on addressing the specific configuration parameters that enable the flaw while maintaining network functionality. Organizations should immediately upgrade their Cisco Wireless LAN Controllers and Aironet Access Points to software releases version 8.5.110.0 or later, which contain the necessary patches to resolve the authentication bypass issue. Network administrators should also review their current network configurations to identify and modify any deployments that match the vulnerable criteria, particularly those operating in FlexConnect Mode with NAT, central switching, and Split Tunnel ACL configurations. The implementation of additional network segmentation and access control measures can provide defense-in-depth protection against exploitation attempts, while continuous monitoring of network traffic for suspicious activities can help detect potential exploitation attempts. Organizations should also consider implementing network access control policies that limit the scope of access granted to wireless clients, reducing the potential impact of successful exploitation. This vulnerability aligns with CWE-284 Access Control Issues and represents a significant concern under the ATT&CK framework's privilege escalation and defense evasion techniques, as it allows attackers to bypass authentication mechanisms and potentially escalate their privileges within the network environment.