CVE-2015-0686 in NX-OS
Summary
by MITRE
Cisco NX-OS 6.1(2)I2(3) on Nexus 9000 devices, when a Reset High Availability (HA) policy is configured, allows remote authenticated users to cause a denial of service (device reload) via unspecified vectors, aka Bug ID CSCuq92240.
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Analysis
by VulDB Data Team • 05/02/2022
The vulnerability described in CVE-2015-0686 represents a critical denial of service weakness affecting Cisco NX-OS software version 6.1(2)I2(3) running on Nexus 9000 series network devices. This flaw specifically manifests when a Reset High Availability policy is configured within the system, creating a condition where authenticated remote attackers can trigger a device reload that effectively disrupts network operations. The vulnerability operates through unspecified vectors that exploit the interaction between the HA policy configuration and the device's handling of certain network events, ultimately leading to an unauthorized system restart that compromises network availability and service continuity. The bug identifier CSCuq92240 further categorizes this issue within Cisco's internal tracking system, indicating its severity and the need for immediate attention.
The technical implementation of this vulnerability stems from improper handling of reset operations within the high availability framework of the NX-OS operating system. When a Reset HA policy is active, the system's response to certain network conditions or management commands can cause the device to enter an unstable state that results in automatic reload. This occurs because the policy configuration does not adequately validate or handle specific reset scenarios, allowing malicious or compromised authenticated users to craft inputs that trigger the problematic code path. The vulnerability demonstrates a classic example of insufficient input validation and error handling within network device management interfaces, where the system fails to properly sanitize or process reset commands that should be safely handled without system disruption. The authentication requirement means that only users with valid credentials can exploit this weakness, but this limitation does not diminish the impact on network availability and operational continuity.
The operational impact of this vulnerability extends beyond simple service disruption to encompass significant business continuity concerns for organizations relying on Nexus 9000 devices for critical network infrastructure. When exploited, the device reload causes complete service interruption until manual intervention occurs to bring the system back online, potentially affecting thousands of connected devices and applications that depend on the network availability. The vulnerability affects the core high availability functionality that organizations depend upon to maintain network resilience, creating a paradox where the very feature designed to ensure system reliability becomes the vector for system instability. Network administrators face the challenge of maintaining service availability while dealing with the potential for unexpected device reloads, particularly during critical operational periods or maintenance windows when the risk of exploitation is highest. This vulnerability can also serve as an entry point for more sophisticated attacks, as the device reload may temporarily disable security monitoring or logging capabilities, providing attackers with window of opportunity for additional exploitation attempts.
Organizations should implement immediate mitigations including upgrading to patched versions of NX-OS software that address the specific handling of reset HA policies and the underlying code paths that trigger device reloads. The recommended approach involves disabling or carefully reviewing any Reset HA policies that are not absolutely necessary for network operations, particularly in environments where authenticated access controls may be compromised. Network security teams should also implement monitoring solutions that can detect anomalous patterns in HA policy usage or device reload events that may indicate exploitation attempts. Additionally, organizations should consider implementing network segmentation and access control measures to limit the number of authenticated users who can configure HA policies, reducing the attack surface for this specific vulnerability. The implementation of these mitigations aligns with industry best practices for managing authenticated remote attack surfaces and follows the principles outlined in the CWE taxonomy for input validation and error handling weaknesses. This vulnerability also demonstrates the importance of comprehensive testing of high availability features under various operational conditions, as the interaction between different system components can create unexpected failure modes that compromise overall system reliability.