CVE-2020-3489 in IOS XE
Summary
by MITRE
Multiple vulnerabilities in the Control and Provisioning of Wireless Access Points (CAPWAP) protocol processing of Cisco IOS XE Software for Cisco Catalyst 9800 Series Wireless Controllers could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition of an affected device. These vulnerabilities are due to insufficient validation of CAPWAP packets. An attacker could exploit these vulnerabilities by sending a malformed CAPWAP packet to an affected device. A successful exploit could allow the attacker to cause the affected device to crash and reload, resulting in a DoS condition on the affected device.
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Analysis
by VulDB Data Team • 09/25/2020
The vulnerability identified as CVE-2020-3489 affects Cisco IOS XE Software running on Cisco Catalyst 9800 Series Wireless Controllers, specifically targeting the Control and Provisioning of Wireless Access Points (CAPWAP) protocol implementation. This represents a significant security weakness in wireless network infrastructure that could be exploited by adjacent attackers to disrupt critical network services. The CAPWAP protocol serves as the primary communication mechanism between wireless access points and wireless controllers, making any vulnerability in its processing particularly dangerous for enterprise wireless networks. The affected devices operate within a controlled network environment where adjacent attackers have physical or network proximity access, which reduces the attack surface complexity while maintaining substantial impact potential.
The technical flaw stems from insufficient input validation within the CAPWAP packet processing logic of the affected Cisco IOS XE Software implementations. When processing incoming CAPWAP packets, the system fails to properly validate packet structures, lengths, or content before attempting to parse and handle the data. This validation gap creates opportunities for malformed packets to be accepted and processed without adequate sanitization, leading to unpredictable behavior in the underlying software stack. The vulnerability manifests when an attacker crafts specifically malformed CAPWAP packets that exploit buffer handling inconsistencies or memory management flaws within the protocol parser. These malformed packets can trigger memory corruption conditions, stack overflows, or other internal state inconsistencies that cause the system to become unstable.
The operational impact of successfully exploiting CVE-2020-3489 results in a complete denial of service condition affecting the wireless controller's availability. When the malformed CAPWAP packet is processed, it causes the affected device to crash and subsequently reload its operating system, effectively taking the wireless infrastructure offline for the duration of the restart process. This disruption affects all wireless services managed by the controller, including authentication, encryption, and access point management functions. The DoS condition can be sustained if the attacker continues sending malformed packets or can be temporary if the device recovers automatically. Network administrators face significant challenges in maintaining wireless service availability, as the attack requires minimal privileges and can be executed from adjacent network segments, making detection and prevention difficult.
Mitigation strategies for CVE-2020-3489 should focus on both immediate defensive measures and long-term architectural improvements. Cisco has released software updates addressing this vulnerability in IOS XE Software releases, which should be applied immediately to affected devices. Network segmentation and access control measures can help reduce the attack surface by limiting adjacent network access to wireless controllers. Implementing network monitoring solutions that can detect anomalous CAPWAP packet patterns or unusual traffic behavior provides early warning capabilities. The vulnerability aligns with CWE-20, representing input validation flaws that lead to system instability, and maps to ATT&CK technique T1499.002 for network denial of service attacks. Organizations should also consider implementing intrusion detection systems specifically configured to monitor for CAPWAP protocol anomalies and establish incident response procedures for rapid recovery from such DoS events.