CVE-2021-1387 in NX-OS
Summary
by MITRE • 02/25/2021
A vulnerability in the network stack of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability exists because the software improperly releases resources when it processes certain IPv6 packets that are destined to an affected device. An attacker could exploit this vulnerability by sending multiple crafted IPv6 packets to an affected device. A successful exploit could cause the network stack to run out of available buffers, impairing operations of control plane and management plane protocols and resulting in a DoS condition. Manual intervention would be required to restore normal operations on the affected device. For more information about the impact of this vulnerability, see the Details section of this advisory.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 03/05/2021
The vulnerability identified as CVE-2021-1387 represents a critical resource management flaw within Cisco NX-OS Software that affects network infrastructure devices operating in enterprise and data center environments. This issue specifically targets the network stack implementation where improper resource handling occurs during processing of IPv6 packets, creating a pathway for remote attackers to disrupt network operations without requiring authentication credentials. The vulnerability exists at the protocol processing level where the software fails to properly manage memory buffers and system resources when encountering specific IPv6 packet structures, leading to resource exhaustion conditions that can severely impact device functionality.
The technical exploitation of this vulnerability occurs through the transmission of specially crafted IPv6 packets to targeted network devices running affected NX-OS versions. When these packets are processed by the network stack, the software's inadequate resource management causes it to release resources improperly, leading to progressive depletion of available buffers within the system. This resource exhaustion directly impacts both the control plane and management plane operations, as these critical system components rely on sufficient buffer availability to maintain normal network operations and administrative access. The flaw demonstrates characteristics consistent with CWE-404, which addresses improper resource release or cleanup, and aligns with ATT&CK technique T1499.004 related to network denial of service attacks that target infrastructure components.
The operational impact of this vulnerability extends beyond simple service interruption to potentially compromise network reliability and availability in mission-critical environments. When exploited successfully, the vulnerability can cause complete network stack disruption, forcing administrators to perform manual intervention procedures including device rebooting and system recovery operations. This disruption affects not only data plane forwarding capabilities but also management plane access, making it extremely difficult for network administrators to diagnose and remediate the issue remotely. The vulnerability's potential for causing widespread service degradation makes it particularly dangerous in large-scale network deployments where multiple affected devices could be simultaneously compromised, leading to cascading failures across network infrastructure.
Organizations should prioritize immediate patch deployment through official Cisco security advisories and ensure comprehensive testing of updates in controlled environments before widespread implementation. Network segmentation and access control measures can provide temporary mitigation by limiting the attack surface and preventing unauthorized access to vulnerable network devices. Monitoring network traffic for unusual IPv6 packet patterns and implementing intrusion detection systems can help identify potential exploitation attempts. Additionally, maintaining detailed network documentation and establishing emergency response procedures will facilitate rapid recovery when incidents occur, as manual intervention requirements make automated remediation challenging. The vulnerability highlights the importance of regular security assessments and timely patch management in maintaining network infrastructure security posture.