CVE-2021-1387

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Exploit odds

1.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-02-24 20:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:31 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.4% in the next 30 days (EPSS).
• Severity: 8.6 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-02-24 20:15 UTC

Last modified

2026-06-17 03:31 UTC

Exploit probability

1.4% · EPSS, next 30 days

Weakness

CWE-401

Record status

Modified

Affected

• Cisco Unified Computing System < 4.0\(4k\)
• Cisco Unified Computing System < 4.1\(1e\)
• Cisco nx-os 7.0\(0\)n1\(1\)
• Cisco nx-os 7.0\(1\)n1\(1\)
• Cisco nx-os 7.0\(2\)n1\(1\)
• Cisco nx-os 7.0\(3\)n1\(1\)
• Cisco nx-os 7.0\(4\)n1\(1\)
• Cisco nx-os 7.0\(4\)n1\(1a\)

Attack profile CVSS 3.1 · 8.6

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-1387.md and follow it. Check whether this project is affected by CVE-2021-1387. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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