CVE-2018-0480 in IOS XE
Summary
by MITRE
A vulnerability in the errdisable per VLAN feature of Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause the device to crash, leading to a denial of service (DoS) condition. The vulnerability is due to a race condition that occurs when the VLAN and port enter an errdisabled state, resulting in an incorrect state in the software. An attacker could exploit this vulnerability by sending frames that trigger the errdisable condition. A successful exploit could allow the attacker to cause the affected device to crash, leading to a DoS condition.
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Analysis
by VulDB Data Team • 05/22/2023
The vulnerability described in CVE-2018-0480 represents a critical denial of service weakness within Cisco IOS XE Software affecting the errdisable per VLAN functionality. This issue specifically targets the software's handling of network port states when multiple VLANs are involved, creating a scenario where the system's internal state management becomes inconsistent. The vulnerability manifests when an attacker exploits a race condition that occurs during the transition of both VLAN and port states into an errdisabled condition, which is a protective mechanism designed to disable faulty network ports to prevent further damage to the network infrastructure. The affected software version demonstrates a fundamental flaw in its state transition logic, where the software fails to properly coordinate the simultaneous disabling of VLAN and port components, leading to unpredictable system behavior.
The technical exploitation of this vulnerability requires an attacker to be in an adjacent network segment, meaning they must have physical or logical access to the same network segment as the target device. This adjacency requirement significantly reduces the attack surface but does not eliminate the threat, particularly in environments where network segmentation is not properly enforced or where attackers have gained access to local network resources. The attacker's method involves sending specific network frames that trigger the errdisable condition, which then activates the race condition within the software's state management system. This race condition creates a scenario where the software's internal data structures become corrupted or inconsistent, ultimately leading to a system crash that results in complete denial of service for the affected device. The vulnerability is particularly concerning because it operates at the network infrastructure level, potentially affecting core network connectivity and availability.
The operational impact of this vulnerability extends beyond simple service disruption, as it can compromise the stability of entire network segments that rely on the affected device for connectivity. When a Cisco device running IOS XE software experiences this crash, network traffic is immediately disrupted, requiring manual intervention to restore normal operations. The recovery process typically involves rebooting the device, which can result in temporary network outages that may affect business operations, especially in mission-critical environments. Network administrators must also consider the potential for cascading failures if the affected device serves as a core router or switch in the network topology, as the DoS condition could propagate throughout the network infrastructure. The vulnerability's impact is further amplified in environments where automated network monitoring systems are not properly configured to detect and respond to such state inconsistencies, potentially leading to extended downtime periods.
Mitigation strategies for CVE-2018-0480 should focus on both immediate protective measures and long-term architectural improvements. Cisco recommends applying the relevant software patches and updates that address the race condition in the errdisable per VLAN feature, which typically involve modifying the state transition logic to properly handle concurrent VLAN and port disabling events. Network segmentation and access control measures should be strengthened to limit the adjacency requirements for potential attackers, including implementing proper VLAN isolation and access control lists that prevent unauthorized network access. Additionally, implementing robust network monitoring systems that can detect unusual state transitions and errdisable conditions can provide early warning of potential exploitation attempts. The vulnerability aligns with CWE-362, which describes race conditions in software systems, and represents a classic example of how improper state management can lead to system instability. From an ATT&CK framework perspective, this vulnerability maps to the privilege escalation and denial of service tactics, as attackers can leverage the flaw to gain control over network availability and potentially move laterally within the network infrastructure. Organizations should also consider implementing redundant network paths and failover mechanisms to minimize the impact of such vulnerabilities on overall network availability and business continuity.