CVE-2013-6683 in NX-OS
Summary
by MITRE
The IPv6 implementation in Cisco NX-OS does not properly handle neighbor-table adjacencies, which allows remote attackers to cause a denial of service (NS processing outage) via a series of malformed packets, aka Bug ID CSCtd15904.
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Analysis
by VulDB Data Team • 06/02/2021
The vulnerability identified as CVE-2013-6683 represents a critical flaw in Cisco NX-OS operating systems that affects IPv6 network infrastructure implementations. This issue stems from improper handling of neighbor table adjacencies within the IPv6 stack, creating a pathway for remote attackers to execute denial of service attacks against network devices. The vulnerability specifically targets the Neighbor Discovery Protocol (NDP) processing mechanisms that are fundamental to IPv6 network operations, where devices maintain neighbor tables to track IPv6 addresses and their corresponding link-layer addresses.
The technical exploitation of this vulnerability occurs through the careful crafting of malformed neighbor discovery packets that trigger unexpected behavior in the NX-OS IPv6 processing engine. When the system receives these specially crafted packets, the neighbor table management logic fails to properly validate or process the adjacency information, leading to system instability and eventual service interruption. This flaw falls under CWE-129, which addresses improper validation of input boundaries, and specifically relates to the improper handling of neighbor table entries in network protocol implementations. The attack vector requires only network access to the affected device, making it particularly dangerous as remote exploitation is possible without authentication or physical access to the network infrastructure.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire network segments that rely on IPv6 connectivity. When the neighbor table processing fails, it can cause cascading effects throughout the network infrastructure, as devices lose the ability to properly communicate with their neighbors and maintain routing information. This vulnerability directly maps to ATT&CK technique T1498, which describes denial of service attacks that target network infrastructure components. The consequences include complete loss of IPv6 connectivity for affected devices, requiring manual intervention to restore normal operations and potentially causing extended downtime for network services that depend on IPv6 addressing.
Organizations affected by this vulnerability should implement immediate mitigations including applying the relevant Cisco security patches and updates that address the neighbor table processing logic. Network administrators should also consider implementing access control lists to filter neighbor discovery traffic and monitor for unusual patterns of neighbor table updates. The recommended approach includes configuring the affected NX-OS devices with proper neighbor table entry validation and implementing rate limiting for neighbor discovery messages. Additionally, organizations should establish monitoring procedures to detect potential exploitation attempts through abnormal neighbor table behavior and ensure that network devices are regularly updated with the latest security patches to prevent similar vulnerabilities from being exploited in the future.