CVE-2022-20728 in Access Point
Summary
by MITRE • 09/30/2022
A vulnerability in the client forwarding code of multiple Cisco Access Points (APs) could allow an unauthenticated, adjacent attacker to inject packets from the native VLAN to clients within nonnative VLANs on an affected device. This vulnerability is due to a logic error on the AP that forwards packets that are destined to a wireless client if they are received on the native VLAN. An attacker could exploit this vulnerability by obtaining access to the native VLAN and directing traffic directly to the client through their MAC/IP combination. A successful exploit could allow the attacker to bypass VLAN separation and potentially also bypass any Layer 3 protection mechanisms that are deployed.
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Analysis
by VulDB Data Team • 10/29/2022
This vulnerability exists within the client forwarding mechanisms of Cisco Access Points and represents a significant security flaw that undermines fundamental network segmentation principles. The issue stems from a logical error in how the access point processes incoming packets, specifically when handling traffic destined for wireless clients. When packets arrive on the native VLAN interface, the AP incorrectly forwards them to wireless clients regardless of whether those clients belong to the native VLAN or other nonnative VLANs. This behavior creates a pathway for attackers to exploit the inherent trust relationships between network segments, effectively allowing unauthorized access to devices that should remain isolated within their designated VLAN boundaries.
The technical implementation of this vulnerability demonstrates a clear violation of network security architecture principles, particularly concerning VLAN isolation and Layer 2 security boundaries. Cisco Access Points are designed to maintain strict separation between different VLANs to prevent lateral movement and unauthorized access between network segments. However, this logic error enables an attacker who gains access to the native VLAN to inject packets directly into the wireless client network, bypassing the normal VLAN filtering mechanisms. The vulnerability specifically affects the packet forwarding code within the AP's network stack, where the device fails to properly validate the VLAN membership of incoming packets before forwarding them to wireless clients.
From an operational impact perspective, this vulnerability creates a serious threat to network security posture, particularly in environments where VLAN segmentation is critical for protecting sensitive data and systems. An attacker positioned within the same physical network segment as the access point can exploit this weakness to gain unauthorized access to clients within nonnative VLANs, potentially accessing systems that should be protected by network segmentation controls. This exploitation capability extends beyond simple packet injection to potentially bypass Layer 3 protection mechanisms that are typically deployed to prevent cross-segment communication. The vulnerability is particularly concerning because it operates at the Layer 2 level, making it difficult to detect through traditional network monitoring tools that focus on higher-level protocols and Layer 3 filtering mechanisms.
The security implications of CVE-2022-20728 align with several ATT&CK framework techniques including T1046 Network Service Scanning and T1562.007 Impair Command and Control Channel, as attackers can use this vulnerability to expand their network reach and potentially establish persistent access to multiple network segments. From a CWE perspective, this vulnerability maps to CWE-284 Improper Access Control, specifically in the context of network device configuration and packet forwarding logic. The flaw represents a classic case of insufficient validation of packet sources and destinations, where the access point fails to properly enforce VLAN boundaries during packet forwarding operations. Organizations with multiple VLAN deployments are particularly at risk, as this vulnerability effectively nullifies the security benefits of VLAN segmentation and creates a backdoor for attackers to traverse network perimeters that should remain protected. Mitigation strategies should include immediate firmware updates from Cisco, implementation of additional network segmentation controls, and enhanced monitoring of VLAN boundary traffic to detect anomalous packet forwarding behavior.
This vulnerability highlights the critical importance of proper network device configuration and the potential security implications of seemingly minor logic errors in network infrastructure components. The flaw demonstrates how a single incorrect assumption in packet forwarding logic can compromise an entire network segmentation strategy, emphasizing the need for comprehensive security testing of network device firmware and code. Network administrators should consider implementing additional security controls beyond traditional VLAN configurations to protect against such vulnerabilities, including MAC address filtering, wireless intrusion detection systems, and regular security assessments of network infrastructure components. The vulnerability also underscores the necessity of maintaining current firmware versions and implementing robust patch management processes to ensure that known security flaws are promptly addressed.