CVE-2021-1229 in NX-OS
Summary
by MITRE • 02/25/2021
A vulnerability in ICMP Version 6 (ICMPv6) processing in Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a slow system memory leak, which over time could lead to a denial of service (DoS) condition. This vulnerability is due to improper error handling when an IPv6-configured interface receives a specific type of ICMPv6 packet. An attacker could exploit this vulnerability by sending a sustained rate of crafted ICMPv6 packets to a local IPv6 address on a targeted device. A successful exploit could allow the attacker to cause a system memory leak in the ICMPv6 process on the device. As a result, the ICMPv6 process could run out of system memory and stop processing traffic. The device could then drop all ICMPv6 packets, causing traffic instability on the device. Restoring device functionality would require a device reboot.
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Analysis
by VulDB Data Team • 03/05/2021
This vulnerability resides in the ICMPv6 processing functionality of Cisco NX-OS Software, representing a critical flaw that enables unauthenticated remote attackers to induce gradual memory depletion through carefully crafted network packets. The issue manifests when IPv6-configured interfaces encounter specific ICMPv6 packet types, triggering improper error handling mechanisms within the software's network stack. This memory leak occurs incrementally over time, making the attack subtle yet potentially devastating for network infrastructure availability. The vulnerability specifically targets the ICMPv6 process within the operating system, where inadequate input validation and error management allow malicious packet sequences to consume system resources without proper termination or cleanup procedures.
The operational impact of this vulnerability extends beyond simple resource exhaustion, creating cascading effects that compromise network stability and service availability. When the ICMPv6 process begins consuming system memory, it gradually depletes available resources until the process becomes unable to handle incoming traffic effectively. This degradation manifests as complete packet dropping for ICMPv6 traffic, effectively isolating the device from critical network management functions that rely on IPv6 communication protocols. The memory leak behavior creates a persistent threat that can accumulate over extended periods, making it particularly dangerous in production environments where continuous uptime is essential for network operations. Network administrators face the challenge of identifying this slow-acting attack pattern, as the symptoms may not immediately indicate a security compromise but rather appear as performance degradation.
From a cybersecurity perspective, this vulnerability aligns with CWE-400, which addresses unrestricted resource consumption, and represents a classic example of a denial of service attack that leverages protocol implementation flaws. The attack vector operates entirely through network communication without requiring authentication credentials, making it particularly dangerous in environments where network interfaces are exposed to untrusted networks. The ATT&CK framework categorizes this as a resource exhaustion technique under the system service compromise tactic, where attackers target fundamental network protocols to disrupt service availability. The sustained packet rate required for exploitation suggests that this vulnerability could be weaponized through automated attack tools, potentially enabling large-scale disruption of network services across multiple devices simultaneously. This attack pattern demonstrates the importance of robust error handling and input validation in network protocol implementations, particularly for IPv6 stacks that are increasingly prevalent in modern network infrastructures.
Mitigation strategies should focus on implementing immediate network segmentation controls to limit exposure of vulnerable devices to untrusted network segments. Network administrators should consider disabling IPv6 functionality on interfaces where it is not required, effectively removing the attack surface entirely. Configuration changes such as implementing rate limiting for ICMPv6 traffic and establishing monitoring thresholds for memory usage can help detect exploitation attempts before they cause significant disruption. The Cisco security advisory recommends applying the latest software patches that address the specific error handling deficiencies in the ICMPv6 processing module. Additionally, implementing network access control lists that filter ICMPv6 traffic based on source addresses and packet characteristics can provide additional protective layers. Regular network monitoring should include memory utilization tracking for network devices, with automated alerts when memory consumption exceeds predetermined thresholds, allowing for proactive intervention before complete service degradation occurs.