CVE-2020-3273 in Wireless LAN Controller
Summary
by MITRE
A vulnerability in the 802.11 Generic Advertisement Service (GAS) frame processing function of Cisco Wireless LAN Controller (WLC) Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS). The vulnerability is due to incomplete input validation of the 802.11 GAS frames that are processed by an affected device. An attacker could exploit this vulnerability by sending a crafted 802.11 GAS frame over the air to an access point (AP), and that frame would then be relayed to the affected WLC. Also, an attacker with Layer 3 connectivity to the WLC could exploit this vulnerability by sending a malicious 802.11 GAS payload in a Control and Provisioning of Wireless Access Points (CAPWAP) packet to the device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS.
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Analysis
by VulDB Data Team • 04/16/2020
The vulnerability identified as CVE-2020-3273 represents a critical denial of service weakness within Cisco Wireless LAN Controller software that exploits the 802.11 Generic Advertisement Service frame processing mechanism. This flaw exists in the wireless infrastructure's handling of network advertisements and is classified under CWE-20, which denotes improper input validation, making it a fundamental security weakness that affects the core processing capabilities of the affected devices. The vulnerability specifically targets the Generic Advertisement Service frames that are part of the IEEE 802.11 standard, which are used for various wireless network operations including service discovery and network information exchange.
The technical implementation of this vulnerability stems from insufficient validation of input data within the 802.11 GAS frame processing logic. When an access point receives a crafted GAS frame, it processes this frame and forwards it to the Wireless LAN Controller where the incomplete validation allows maliciously constructed frames to trigger unexpected behavior. The vulnerability manifests when the WLC receives either wireless frames transmitted through the air from an access point or when an attacker with Layer 3 connectivity sends malicious payloads within CAPWAP protocol packets directly to the controller. This dual exploitation vector significantly increases the attack surface as it can be leveraged both from wireless air interfaces and network layer connections.
From an operational perspective, the impact of successful exploitation results in complete service disruption through device reload operations that effectively deny network access to all connected wireless clients. The denial of service condition is particularly severe in enterprise environments where wireless networks support critical business operations, as it can lead to complete network outages affecting productivity and business continuity. The vulnerability's remote nature means that attackers do not require physical access or local network privileges to exploit the weakness, making it particularly dangerous in public or shared wireless environments. This characteristic aligns with ATT&CK technique T1499.001, which describes network denial of service attacks that can be executed remotely.
The exploitation process requires minimal privileges and can be automated, making it attractive to threat actors seeking to disrupt wireless services. Network administrators should note that the vulnerability affects multiple Cisco WLC software versions and can be triggered through legitimate network traffic flows, making detection difficult during active exploitation. The lack of authentication requirements for exploitation means that even unauthorized users can potentially cause service disruption, representing a significant risk to wireless infrastructure security. Mitigation strategies should include implementing network segmentation, deploying wireless intrusion detection systems, and applying Cisco's official security patches to address the input validation deficiencies in the affected software components.