CVE-2018-0331 in NX-OS
Summary
by MITRE
A vulnerability in the Cisco Discovery Protocol (formerly known as CDP) subsystem of devices running, or based on, Cisco NX-OS Software contain a vulnerability that could allow an unauthenticated, adjacent attacker to create a denial of service (DoS) condition. The vulnerability is due to a failure to properly validate certain fields within a Cisco Discovery Protocol message prior to processing it. An attacker with the ability to submit a Cisco Discovery Protocol message designed to trigger the issue could cause a DoS condition on an affected device while the device restarts. This vulnerability affects Firepower 4100 Series Next-Generation Firewall, Firepower 9300 Security Appliance, MDS 9000 Series Multilayer Director Switches, Nexus 1000V Series Switches, Nexus 1100 Series Cloud Services Platforms, Nexus 2000 Series Switches, Nexus 3000 Series Switches, Nexus 3500 Platform Switches, Nexus 3600 Platform Switches, Nexus 5500 Platform Switches, Nexus 5600 Platform Switches, Nexus 6000 Series Switches, Nexus 7000 Series Switches, Nexus 7700 Series Switches, Nexus 9000 Series Switches in NX-OS mode, Nexus 9500 R-Series Line Cards and Fabric Modules, UCS 6100 Series Fabric Interconnects, UCS 6200 Series Fabric Interconnects, UCS 6300 Series Fabric Interconnects. Cisco Bug IDs: CSCvc89242, CSCve40943, CSCve40953, CSCve40965, CSCve40970, CSCve40978, CSCve40992, CSCve41000, CSCve41007.
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Analysis
by VulDB Data Team • 03/28/2023
The vulnerability identified as CVE-2018-0331 resides within the Cisco Discovery Protocol (CDP) subsystem of various networking devices running Cisco NX-OS software. This flaw represents a critical security weakness that allows unauthenticated attackers positioned in the same network segment to induce denial of service conditions on affected systems. The vulnerability stems from insufficient input validation mechanisms within the CDP message processing pipeline, specifically failing to properly validate certain fields before they are processed by the device. The CDP protocol operates at the data link layer and is designed to provide information about directly connected Cisco devices, making it a fundamental component of network discovery and management operations. When an attacker crafts a malicious CDP message with malformed or specially constructed fields, the device's processing routine encounters a condition that triggers an unexpected behavior leading to system restart.
The technical implementation of this vulnerability manifests when the affected device receives a specially crafted CDP packet that contains fields which exceed expected parameter limits or contain unexpected data types. This improper validation leads to a buffer overflow condition or other memory corruption scenarios that cause the device's operating system to crash and subsequently restart. The restart process effectively creates a denial of service condition that disrupts network connectivity and service availability for the affected device. This vulnerability affects a broad range of Cisco networking equipment including firewalls, switches, and fabric interconnects across multiple product lines, indicating a widespread impact across the Cisco ecosystem. The affected devices include Firepower 4100 Series Next-Generation Firewalls, various Nexus series switches from 1000V through 9500 R-Series, MDS 9000 Series Multilayer Director Switches, and UCS fabric interconnects, demonstrating the vulnerability's reach across different network infrastructure components.
The operational impact of CVE-2018-0331 extends beyond simple service disruption to potentially compromise network stability and availability. Network administrators face the challenge of maintaining continuous operations when an adjacent attacker can cause repeated device restarts through simple network packet injection. This vulnerability particularly affects environments where network segmentation is minimal or where adjacent network access cannot be adequately controlled, as the attack requires only local network access rather than sophisticated privileges. The DoS condition creates cascading effects throughout the network topology, potentially disrupting communication paths, causing network reconvergence, and affecting dependent services that rely on the affected devices. Organizations operating in regulated environments or requiring high availability may face compliance violations or service level agreement breaches when such vulnerabilities are exploited.
Mitigation strategies for CVE-2018-0331 should focus on both immediate defensive measures and long-term architectural improvements. Network administrators should implement network segmentation controls to limit adjacent network access to critical infrastructure, particularly disabling CDP on interfaces that do not require it for network management purposes. Cisco recommends applying the relevant software patches and updates provided in their security advisories, which typically include enhanced input validation routines and improved error handling for CDP message processing. The implementation of network access control lists and firewall rules can help filter or block suspicious CDP traffic, while monitoring systems should be deployed to detect unusual patterns of CDP message traffic that might indicate exploitation attempts. Additionally, organizations should conduct regular vulnerability assessments and penetration testing to identify similar weaknesses in their network infrastructure and ensure that network devices are properly configured to minimize attack surface exposure. This vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and maps to ATT&CK technique T1071.004 for application layer protocol manipulation, highlighting the need for comprehensive network security controls that address both network layer and application layer vulnerabilities.