CVE-2012-6396 in NX-OS
Summary
by MITRE
Cisco NX-OS on Nexus 7000 series switches does not properly handle certain line-card replacements, which might allow remote authenticated users to cause a denial of service (memory consumption) via a crafted configuration that references interfaces that do not exist on the new card, aka Bug ID CSCud44300.
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Analysis
by VulDB Data Team • 12/21/2021
The vulnerability identified as CVE-2012-6396 affects Cisco NX-OS operating system running on Nexus 7000 series network switches. This issue stems from improper handling of line-card replacement operations within the switch's configuration management system. When administrators replace line cards in these switches, the system fails to properly validate interface references in existing configurations, creating a critical operational weakness that can be exploited by authenticated attackers.
The technical flaw manifests when a line card is removed and replaced with a different model or when a card is physically swapped. During this process, the NX-OS software does not adequately validate interface references within existing configurations that may no longer be valid on the new line card. Specifically, when a configuration contains references to interfaces that do not exist on the replacement card, the system enters an infinite loop or consumes excessive memory resources while attempting to process these invalid references. This behavior represents a classic denial of service vulnerability that can be triggered through crafted configuration commands.
The operational impact of this vulnerability is significant for network infrastructure reliability and availability. Remote authenticated users who can access the switch's management interface can exploit this weakness to consume memory resources until the system becomes unresponsive or crashes entirely. This creates a denial of service condition that can disrupt network services and potentially require manual intervention to restore normal operations. The vulnerability is particularly dangerous in production environments where network switches are critical to maintaining connectivity and business operations. The issue is classified under CWE-399 as a Resource Management Error, specifically related to insufficient resource management during system operations.
The exploitation of this vulnerability aligns with techniques described in the MITRE ATT&CK framework under the Tactic of Resource Hijacking and Denial of Service. Attackers can leverage this weakness to cause sustained disruption of network services, potentially affecting multiple network segments if the compromised switch serves as a core routing or switching device. The vulnerability affects the switch's configuration management subsystem and can be triggered through legitimate administrative commands that reference non-existent interfaces, making it particularly insidious as it may appear to be a normal administrative operation.
Organizations should implement immediate mitigations including applying the relevant Cisco security patches and updates that address this specific line-card replacement handling issue. Network administrators should also implement monitoring procedures to detect unusual memory consumption patterns and configure proper access controls to limit who can make configuration changes to critical network infrastructure. Additionally, implementing staged line-card replacement procedures that validate configuration references before card replacement can help prevent exploitation of this vulnerability. Regular vulnerability assessments and network segmentation strategies should be employed to minimize the potential impact of such attacks on overall network availability and security posture.