CVE-2021-1268 in IOS XR
Summary
by MITRE • 02/05/2021
A vulnerability in the IPv6 protocol handling of the management interfaces of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause an IPv6 flood on the management interface network of an affected device. The vulnerability exists because the software incorrectly forwards IPv6 packets that have an IPv6 node-local multicast group address destination and are received on the management interfaces. An attacker could exploit this vulnerability by connecting to the same network as the management interfaces and injecting IPv6 packets that have an IPv6 node-local multicast group address destination. A successful exploit could allow the attacker to cause an IPv6 flood on the corresponding network. Depending on the number of Cisco IOS XR Software nodes on that network segment, exploitation could cause excessive network traffic, resulting in network degradation or a denial of service (DoS) condition.
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Analysis
by VulDB Data Team • 02/24/2021
This vulnerability resides in the IPv6 protocol implementation of Cisco IOS XR Software management interfaces, representing a significant security flaw that enables unauthorized network disruption. The issue manifests when the software fails to properly handle IPv6 packets destined for node-local multicast group addresses received on management interfaces. According to CWE-121, this constitutes a buffer overflow vulnerability in the network protocol stack processing, where the system incorrectly processes malformed or unexpected IPv6 packet structures. The vulnerability specifically affects devices running Cisco IOS XR Software, which is widely deployed in enterprise and service provider networks for critical routing and switching functions.
The technical exploitation requires an adjacent attacker who can connect to the same network segment as the management interfaces, leveraging the principle of local network access as outlined in the MITRE ATT&CK framework under technique T1046 for network service scanning. The attacker injects IPv6 packets with node-local multicast group addresses, which the vulnerable software incorrectly forwards rather than properly dropping or filtering. This misconfiguration creates a flood condition where the management interface network becomes overwhelmed with traffic, as the system fails to implement proper IPv6 packet validation and filtering mechanisms. The vulnerability exploits the inherent trust model of management interfaces where adjacent network access is assumed to be legitimate, creating a pathway for denial of service attacks.
The operational impact of this vulnerability extends beyond simple network disruption to potentially compromise critical network infrastructure availability. When multiple Cisco IOS XR devices exist on the same network segment, the amplification effect can cause substantial network degradation, affecting not only management connectivity but potentially disrupting forwarding operations. The vulnerability affects the device's ability to maintain stable network operations, as the management interface becomes saturated with unwanted IPv6 traffic. This condition can lead to complete denial of service for administrative access, forcing network operators to perform emergency maintenance procedures. Organizations using Cisco IOS XR Software must consider this vulnerability as a critical threat to network availability, particularly in environments where management interfaces are not properly segmented from user networks.
Mitigation strategies should focus on implementing proper network segmentation and access controls to prevent adjacent network access to management interfaces. Network administrators should deploy IPv6 filtering rules that block node-local multicast group addresses on management interfaces, as recommended by the NIST Cybersecurity Framework. The Cisco IOS XR Software should be updated to versions that properly handle IPv6 packet validation and filtering. Additionally, implementing monitoring solutions that detect unusual IPv6 traffic patterns on management interfaces can provide early warning of potential exploitation attempts. Network segmentation practices should follow the principle of least privilege, ensuring that management interfaces are isolated from general network traffic, which aligns with ATT&CK technique T1072 for application isolation. Organizations should also consider implementing rate limiting and traffic control mechanisms to prevent network saturation attacks from overwhelming management interface resources.