CVE-2018-0235 in Wireless LAN Controller
Summary
by MITRE
A vulnerability in the 802.11 frame validation functionality of the Cisco Wireless LAN Controller (WLC) could allow an unauthenticated, adjacent attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. The vulnerability is due to incomplete input validation of certain 802.11 management information element frames that an affected device receives from wireless clients. An attacker could exploit this vulnerability by sending a malformed 802.11 management frame to an affected device. A successful exploit could allow the attacker to cause the affected device to reload unexpectedly, resulting in a DoS condition. This vulnerability affects only Cisco Wireless LAN Controllers that are running Cisco Mobility Express Release 8.5.103.0. Cisco Bug IDs: CSCvg07024.
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Analysis
by VulDB Data Team • 02/01/2020
The vulnerability described in CVE-2018-0235 represents a critical denial of service weakness within Cisco's Wireless LAN Controller ecosystem, specifically targeting devices operating under Cisco Mobility Express Release 8.5.103.0. This flaw resides in the 802.11 frame validation mechanisms that govern how wireless access points process management information element frames from connected clients. The vulnerability stems from inadequate input validation procedures that fail to properly sanitize or verify the structure and content of incoming 802.11 management frames, creating an exploitable entry point for malicious actors within the physical proximity of the affected infrastructure.
The technical exploitation of this vulnerability requires an attacker to craft and transmit specifically malformed 802.11 management frames to the targeted Cisco WLC device. These frames contain improperly structured information elements that trigger the device's validation routines to malfunction, ultimately causing the wireless controller to undergo an unexpected system reload. The flaw operates at the layer 2 wireless protocol level, specifically targeting the management frame processing capabilities that handle client association, authentication, and other wireless network control functions. According to the Common Weakness Enumeration framework, this vulnerability maps to CWE-20, which describes "Improper Input Validation" as a fundamental weakness that allows malformed inputs to disrupt system operations.
The operational impact of this vulnerability extends beyond simple service disruption, as the unexpected device reloads can cause significant network instability and temporary loss of wireless connectivity for all connected clients. Network administrators may experience prolonged periods of service unavailability while the affected WLCs restart and re-establish their wireless network configurations. The vulnerability's adjacency requirement means that attackers must be physically present within the wireless network's coverage area, typically within 100 meters of the targeted access point, which limits the attack surface but does not eliminate the risk. This characteristic aligns with ATT&CK technique T1499.001, which covers "Network Denial of Service" through physical proximity attacks.
Cisco has identified this specific vulnerability as CSCvg07024 and has provided targeted remediation through software updates and patches for affected systems. The vulnerability affects only devices running Cisco Mobility Express Release 8.5.103.0, making it a release-specific issue that requires careful version verification before applying mitigation measures. Organizations should implement network segmentation and monitoring to detect anomalous wireless traffic patterns that might indicate exploitation attempts. The recommended mitigation strategies include applying the latest software patches from Cisco, implementing wireless intrusion detection systems to monitor for malformed frames, and establishing proper network access controls to limit physical access to wireless infrastructure. Additionally, network administrators should consider deploying redundant wireless controllers to maintain service availability during patching operations and implement comprehensive monitoring to detect unexpected device reboots that could indicate exploitation attempts.