CVE-2024-6858 in EOS
Summary
by MITRE • 06/05/2026
In Arista’s EOS when in 802.1X mode, multi-auth unauthenticated hosts might be allowed access to a switch port if there exists an EAPOL capable device in the fallback VLAN.
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Analysis
by VulDB Data Team • 06/05/2026
This vulnerability exists within Arista Enterprise Operating System (EOS) when operating in 802.1X authentication mode, specifically affecting the multi-authentication handling process for unauthenticated hosts. The flaw stems from improper VLAN assignment logic where the system fails to correctly isolate unauthenticated devices when EAPOL (Extensible Authentication Protocol over LAN) capable devices are present in the fallback VLAN. When such devices exist in the fallback VLAN, the authentication mechanism incorrectly permits multiple unauthenticated hosts to gain access to the switch port, creating a potential security breach.
The technical implementation of this vulnerability relates to the IEEE 802.1X standard enforcement within the network switch's authentication framework. The flaw manifests when the switch processes authentication requests from multiple hosts simultaneously, where the fallback VLAN mechanism does not properly maintain segregation between authenticated and unauthenticated devices. This occurs because the system's state management does not adequately track the authentication status of hosts when EAPOL communication occurs in the fallback VLAN context, leading to a misconfiguration where unauthorized access is granted. The vulnerability is classified under CWE-284 Access Control Issues, specifically related to insufficient access control mechanisms in network device authentication.
The operational impact of this vulnerability extends beyond simple unauthorized access, potentially allowing attackers to establish persistent network footholds through unauthorized device connections. An attacker could exploit this by connecting multiple unauthenticated devices to a port where an EAPOL capable device exists in the fallback VLAN, thereby bypassing the intended authentication controls. This creates a vector for lateral movement within the network as unauthorized devices can communicate with other network segments that should be restricted to authenticated users only. The vulnerability is particularly concerning in enterprise environments where network segmentation is critical for security posture.
Mitigation strategies should focus on implementing proper VLAN isolation and authentication state management within the switch configuration. Network administrators should ensure that fallback VLANs are properly configured to prevent EAPOL capable devices from existing in the same VLAN as unauthenticated hosts. Additionally, implementing proper access control lists and port security measures can help prevent unauthorized device connections. The recommended approach includes disabling unnecessary EAPOL capabilities in fallback VLANs, implementing strict VLAN assignments, and regularly auditing network access controls. This vulnerability aligns with ATT&CK technique T1078 Valid Accounts, as it allows unauthorized access through legitimate authentication mechanisms that should have prevented such access, potentially enabling credential theft or privilege escalation attacks.