CVE-2020-3552 in Aironet Access Point
Summary
by MITRE
A vulnerability in the Ethernet packet handling of Cisco Aironet Access Points (APs) Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to insufficient input validation. An attacker could exploit this vulnerability by connecting as a wired client to the Ethernet interface of an affected device and sending a series of specific packets within a short time frame. A successful exploit could allow the attacker to cause a NULL pointer access that results in a reload of the affected device.
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Analysis
by VulDB Data Team • 09/25/2020
The vulnerability identified as CVE-2020-3552 affects Cisco Aironet Access Points where improper input validation in the Ethernet packet handling mechanism creates a path for denial of service attacks. This weakness specifically targets the software implementation within wireless access points that process incoming Ethernet traffic from wired clients. The flaw exists in the device's packet processing logic where it fails to adequately validate incoming data structures before attempting to process them, creating a condition where malformed or specially crafted packets can trigger unexpected behavior. The vulnerability is particularly concerning because it requires minimal privileges to exploit, as no authentication is required for an adjacent attacker to initiate the attack vector through the wired Ethernet interface.
The technical exploitation of this vulnerability follows a precise pattern where an attacker must physically connect to the wired Ethernet port of an affected access point and transmit a sequence of malicious packets in rapid succession. This attack methodology aligns with the ATT&CK framework's privilege escalation and denial of service techniques, specifically mapping to the T1499.004 sub-technique related to network denial of service. The exploitation process triggers a NULL pointer dereference condition within the affected device's software stack, causing the system to attempt to access memory at a null address. This memory access violation forces the device to restart its operating system components, resulting in the device reloading its software and temporarily becoming unavailable to legitimate users. The vulnerability's classification as CWE-125, "Out-of-bounds Read," or CWE-476, "NULL Pointer Dereference," demonstrates the fundamental nature of the software flaw that allows this attack to succeed.
The operational impact of CVE-2020-3552 extends beyond simple service disruption, as the affected access points may experience repeated reload cycles that could lead to extended network outages and service degradation for wireless users. Network administrators face the challenge of identifying and mitigating this vulnerability without disrupting legitimate wired client connections, as the attack requires physical proximity to the device. The vulnerability affects multiple Cisco Aironet models and software versions, creating widespread exposure across enterprise and corporate wireless networks where access point security may be insufficiently addressed. Organizations with wireless infrastructure that relies heavily on these access points for network connectivity face significant risk, as the DoS condition can be sustained for extended periods if not properly mitigated.
Mitigation strategies for CVE-2020-3552 focus on both immediate defensive measures and long-term architectural improvements. Network segmentation and access control measures should be implemented to restrict physical access to wired Ethernet ports on access points, preventing unauthorized clients from connecting and initiating attacks. Cisco recommends applying the latest software patches that include fixes for input validation and memory handling in the Ethernet packet processing code. The implementation of network access control lists and port security features can help detect and prevent unusual packet patterns that may indicate exploitation attempts. Additionally, monitoring systems should be configured to detect rapid connection and disconnection events on wired ports, which could indicate an active attack. Organizations should also consider implementing redundant access point configurations and failover mechanisms to minimize the impact of successful DoS attacks. The vulnerability underscores the importance of secure coding practices and input validation, particularly in network infrastructure devices where the consequences of memory corruption can result in complete system restarts and service interruptions.