Is CVE-2021-1387 actively exploited?

No active exploitation of CVE-2021-1387 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-1387 be exploited remotely?

Yes. CVE-2021-1387 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2021-1387?

CVE-2021-1387 has a CVSS score of 8.6 (HIGH).

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HIGH

CVE-2021-1387

CWE-401Published: February 24, 2021· Updated: Jun 17, 2026

8.6

CVSS v3.1

Official Description

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.

NVD Source

Technical Analysis

CVE-2021-1387 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 8.6.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.