CVE-2015-4197 in NX-OS
Summary
by MITRE
Cisco NX-OS 5.2(5) on Nexus 7000 devices allows remote attackers to cause a denial of service (device crash) by sending a malformed LLDP packet on the local network, aka Bug ID CSCud89415.
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Analysis
by VulDB Data Team • 05/17/2018
Cisco NX-OS software version 5.2(5) running on Nexus 7000 series switches contains a critical vulnerability that enables remote attackers to execute a denial of service attack through manipulation of Link Layer Discovery Protocol packets. This vulnerability specifically affects the processing of malformed LLDP frames within the device's network infrastructure, creating a condition where legitimate network operations can be disrupted through carefully crafted malicious packets. The flaw exists in the LLDP packet parsing mechanism, where insufficient input validation allows malformed data structures to trigger unexpected behavior in the switch's control plane processing. The vulnerability is classified under CWE-129 as an insufficient input validation issue, where the system fails to properly validate the length and structure of received LLDP frames before processing them. Attackers can exploit this weakness by transmitting specially crafted LLDP packets that contain malformed fields or unexpected data sequences, which when processed by the vulnerable switch cause the device to crash and reboot automatically. This type of attack falls under the ATT&CK technique T1499.004 for network denial of service, specifically targeting network infrastructure devices to disrupt availability. The operational impact of this vulnerability extends beyond simple service interruption as it affects the core network fabric of data centers and enterprise networks that rely on Nexus 7000 switches for critical routing and switching functions. When exploited, the device crash results in complete loss of network connectivity for all traffic passing through the affected switch, potentially causing cascading failures throughout the network infrastructure. The vulnerability is particularly dangerous because it requires no authentication or privileged access to exploit, making it accessible to any attacker on the local network segment. Network administrators must understand that this flaw represents a fundamental weakness in the switch's packet processing architecture where malformed input can directly translate into system instability. The affected software version 5.2(5) indicates that this vulnerability was present in a widely deployed release, suggesting that many enterprise and data center networks were potentially exposed to this risk. The Cisco bug ID CSCud89415 specifically identifies this issue as a parsing error in the LLDP implementation, where the system fails to properly handle edge cases in LLDP packet format validation. Organizations using affected hardware should immediately implement mitigation strategies including network segmentation to isolate vulnerable switches, implementing LLDP packet filtering rules, and applying the appropriate Cisco software patches to address the input validation flaw. The vulnerability demonstrates the critical importance of proper input validation in network infrastructure devices, where malformed packets from untrusted sources can be exploited to compromise system stability and availability. This flaw exemplifies how seemingly benign network protocols like LLDP can become attack vectors when proper defensive measures are not implemented in the device firmware. The attack vector requires only local network access, making it particularly concerning for environments where network segmentation is insufficient or where attackers have gained access to network segments containing vulnerable equipment. Security teams must consider this vulnerability as part of their broader network resilience planning, ensuring that network infrastructure devices are regularly updated and that proper monitoring is in place to detect potential exploitation attempts. The remediation process requires careful planning since switch reboots can disrupt network operations, necessitating coordinated maintenance windows to apply the necessary patches and prevent exploitation of this denial of service vulnerability.