CVE-2018-0372 in NX-OS
Summary
by MITRE
A vulnerability in the DHCPv6 feature of the Cisco Nexus 9000 Series Fabric Switches in Application-Centric Infrastructure (ACI) Mode could allow an unauthenticated, remote attacker to cause the device to run low on system memory, which could result in a Denial of Service (DoS) condition on an affected system. The vulnerability is due to improper memory management when DHCPv6 packets are received on an interface of the targeted device. An attacker could exploit this vulnerability by sending a high number of malicious DHCPv6 packets to be processed by an affected device. A successful exploit could allow the attacker to cause the system to run low on memory, which could cause an eventual reboot of an affected device. The vulnerability only applies to IPv6 protocol packets and not for IPv4 protocol packets. This vulnerability affects Cisco Nexus 9000 Series Fabric Switches in ACI Mode running software version 13.0(1k). The vulnerability can only be exploited when unicast routing is enabled on the Bridge Domain (BD). DHCP and DHCP relay do not have to be configured for the vulnerability to be exploited. Cisco Bug IDs: CSCvg38918.
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Analysis
by VulDB Data Team • 04/18/2023
The vulnerability described in CVE-2018-0372 represents a critical memory management flaw within the DHCPv6 implementation of Cisco Nexus 9000 Series Fabric Switches operating in Application-Centric Infrastructure (ACI) mode. This weakness specifically targets the handling of IPv6 protocol packets and demonstrates how improper resource allocation can lead to severe operational disruptions. The vulnerability exists in software version 13.0(1k) and affects devices that have unicast routing enabled on their Bridge Domains, making it particularly concerning for network infrastructure that relies on these switches for critical connectivity functions.
The technical exploitation of this vulnerability occurs through the manipulation of DHCPv6 packet processing mechanisms within the switch's memory management system. When an attacker sends a high volume of malicious DHCPv6 packets to an affected interface, the device fails to properly manage memory allocation during packet processing, leading to progressive memory exhaustion. This improper memory handling stems from inadequate input validation and resource cleanup procedures within the DHCPv6 processing code, creating a condition where memory resources become progressively consumed until the system reaches a critical low-water mark. The vulnerability is classified under CWE-129 as an improper input validation issue and aligns with ATT&CK technique T1499.002 for network denial of service attacks.
The operational impact of this vulnerability extends beyond simple service disruption to potentially causing complete system reboots, which can result in significant network downtime and operational chaos. Network administrators face the challenge of maintaining service availability while dealing with a vulnerability that can be exploited remotely without authentication requirements, making it particularly dangerous in production environments. The fact that this vulnerability specifically targets IPv6 packets while leaving IPv4 protocols unaffected means that organizations must maintain separate security measures for different protocol stacks. The requirement for unicast routing to be enabled on Bridge Domains creates a specific attack surface that network architects must carefully monitor and control, as disabling this feature would prevent exploitation of the vulnerability.
Mitigation strategies for CVE-2018-0372 should focus on immediate software updates and network configuration changes to prevent exploitation. Cisco has released patches addressing this vulnerability through their security advisory process, and organizations must prioritize applying these updates to all affected devices. Network segmentation and access control measures can provide additional defense-in-depth by limiting the interfaces that can receive DHCPv6 traffic. Implementing rate limiting on DHCPv6 packet processing and monitoring memory utilization patterns can help detect potential exploitation attempts. The vulnerability also highlights the importance of network monitoring solutions that can identify unusual traffic patterns and memory consumption spikes, as these indicators may precede a successful DoS attack. Organizations should also consider implementing network access control lists to restrict DHCPv6 traffic sources and reduce the attack surface available to potential adversaries.