CVE-2020-3418 in IOS XE
Summary
by MITRE
A vulnerability in Cisco IOS XE Wireless Controller Software for Cisco Catalyst 9800 Series Routers could allow an unauthenticated, adjacent attacker to send ICMPv6 traffic prior to the client being placed into RUN state. The vulnerability is due to an incomplete access control list (ACL) being applied prior to RUN state. An attacker could exploit this vulnerability by connecting to the associated service set identifier (SSID) and sending ICMPv6 traffic. A successful exploit could allow the attacker to send ICMPv6 traffic prior to RUN state.
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Analysis
by VulDB Data Team • 09/25/2020
The vulnerability identified as CVE-2020-3418 resides within Cisco IOS XE Wireless Controller Software operating on Cisco Catalyst 9800 Series Routers, representing a significant security weakness that undermines network access controls. This flaw specifically targets the wireless controller functionality where access control mechanisms fail to properly enforce restrictions during the device initialization phase. The vulnerability manifests when the wireless controller processes incoming traffic before the client device has transitioned into the RUN operational state, creating a temporal window where unauthorized network access can occur.
The technical root cause of this vulnerability stems from an incomplete access control list implementation that does not adequately filter incoming ICMPv6 traffic during the pre-RUN state period. This incomplete ACL enforcement creates a security gap where adjacent attackers can exploit the temporal inconsistency in the wireless controller's access control mechanisms. The vulnerability specifically affects the wireless service set identifier (SSID) provisioning process where the controller's security policies are not fully applied until after the client device has successfully negotiated its operational state. This design flaw allows attackers to bypass normal access controls by leveraging the pre-RUN state period to inject malicious ICMPv6 traffic into the network infrastructure.
The operational impact of CVE-2020-3418 extends beyond simple unauthorized network access, as it provides attackers with a foothold to potentially escalate their privileges and conduct further malicious activities within the network. Attackers exploiting this vulnerability can send ICMPv6 traffic without authentication, potentially enabling them to perform reconnaissance, disrupt network services, or establish persistent access points within the wireless infrastructure. The adjacent network access requirement means that attackers must be physically present on the same network segment as the affected router, but this proximity requirement does not prevent significant damage since the vulnerability allows for privileged network operations during the client initialization phase. This vulnerability specifically aligns with CWE-284, which addresses improper access control, and represents a classic case of incomplete mediation where security controls are not properly enforced during system transitions.
The exploitation of this vulnerability requires minimal technical expertise and can be accomplished through standard network reconnaissance and packet crafting tools. Attackers can connect to the targeted SSID and send ICMPv6 packets to manipulate the wireless controller's behavior before the client enters its operational state. This attack vector is particularly concerning because it can be executed without requiring authentication credentials, making it accessible to any adjacent network user. The vulnerability's impact is further amplified by the fact that it affects enterprise-grade wireless infrastructure that typically handles sensitive network traffic and user data. Network administrators should consider this vulnerability in the context of ATT&CK framework's T1046 technique for network service scanning, as the ICMPv6 traffic can be used to discover network topology and identify potential targets for further exploitation.
Mitigation strategies for CVE-2020-3418 should focus on implementing immediate software updates from Cisco that address the incomplete ACL enforcement issue in the wireless controller software. Organizations should also consider network segmentation approaches to limit adjacent network access to critical infrastructure components and implement additional monitoring controls to detect anomalous ICMPv6 traffic patterns. The vulnerability's nature suggests that network access control policies should be reviewed and strengthened to ensure that all traffic is properly filtered regardless of the client's operational state. Security teams should also implement network behavior monitoring to detect unauthorized ICMPv6 traffic that could indicate exploitation attempts. Additionally, organizations should verify that their wireless controller configurations properly enforce access controls throughout all operational phases, not just during the RUN state, to prevent similar temporal access control gaps from occurring in other network components.