CVE-2018-0163 in IOS
Summary
by MITRE
A vulnerability in the 802.1x multiple-authentication (multi-auth) feature of Cisco IOS Software could allow an unauthenticated, adjacent attacker to bypass the authentication phase on an 802.1x multi-auth port. The vulnerability is due to a logic change error introduced into the code. An attacker could exploit this vulnerability by trying to access an 802.1x multi-auth port after a successful supplicant has authenticated. An exploit could allow the attacker to bypass the 802.1x access controls and obtain access to the network. Cisco Bug IDs: CSCvg69701.
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Analysis
by VulDB Data Team • 01/17/2020
The vulnerability described in CVE-2018-0163 represents a critical weakness in Cisco IOS Software's implementation of 802.1x multiple-authentication functionality. This flaw specifically targets the authentication phase of network access control mechanisms, creating a pathway for unauthorized network access that directly undermines the security posture of affected networks. The vulnerability stems from a logic error within the codebase that governs how 802.1x multi-auth ports handle authentication sequences, fundamentally compromising the integrity of the access control process.
The technical implementation of this vulnerability involves a specific code modification that alters the expected authentication flow within the 802.1x multi-auth feature. When a legitimate supplicant successfully authenticates to an 802.1x multi-auth port, the system should properly enforce access controls and prevent unauthorized entities from gaining network access. However, due to the introduced logic error, an adjacent attacker can exploit the system by attempting to access the same port after a legitimate authentication has occurred. This creates a window of opportunity where the authentication mechanism fails to properly validate subsequent connection attempts, allowing unauthorized access to bypass the intended security controls.
The operational impact of this vulnerability extends beyond simple network access violations, as it fundamentally undermines the trust model that 802.1x authentication is designed to establish. An attacker exploiting this vulnerability can gain network access without proper authentication credentials, potentially leading to data breaches, lateral movement within the network, and compromise of sensitive systems. The adjacent network access requirement means that attackers must be physically present on the same network segment as the target device, but this proximity requirement does not significantly limit the attack surface given that many network environments have relatively open physical access controls. This vulnerability directly impacts the CIA triad, particularly confidentiality and integrity, as unauthorized entities can access network resources that should remain protected.
Network security professionals should consider this vulnerability in the context of the broader ATT&CK framework, specifically under the techniques related to credential access and lateral movement. The vulnerability aligns with ATT&CK technique T1078 which covers valid accounts and T1021 which covers remote services, as attackers can leverage this weakness to establish unauthorized network presence. From a CWE perspective, this vulnerability maps to CWE-284 which describes improper access control, and potentially CWE-362 which covers concurrent execution with impropper access control. Organizations should implement immediate mitigations including applying Cisco's security patches, reviewing network access control configurations, and implementing additional monitoring for unusual authentication patterns on 802.1x ports. The vulnerability also highlights the importance of proper code review and security testing during software development cycles, particularly for authentication and authorization mechanisms that form the foundation of network security infrastructure.