CVE-2021-1229

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

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: 5.8 MEDIUM (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 nx-os 5.2\(1\)sv5\(1.3a\)
• Cisco nx-os 8.4\(3.53\)
• Cisco nx-os 15.1\(2.31\)

Attack profile CVSS 3.1 · 5.8

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

Low

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-2021-1229.md and follow it. Check whether this project is affected by CVE-2021-1229. 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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