CVE-2021-1229Network attack vector

Service interruption via ICMPv6 memory exhaustion

Published Feb 24, 2021 · Updated Nov 8, 2024

Denial of service in Cisco NX-OS Software allows remote attackers to interrupt ICMPv6 processing by sending crafted packets. Improper error handling in the ICMPv6 process retains allocated memory for each qualifying packet instead of returning it after processing. At least one interface must accept IPv6 traffic, and a sustained packet rate can exhaust the process, destabilize traffic, and require a device reboot.

CVSS severity5.8
Medium
EPSS probability1.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cisco NX-OS Software allows remote attackers to interrupt ICMPv6 processing by sending crafted packets. Improper error handling in the ICMPv6 process retains allocated memory for each qualifying packet instead of returning it after processing. At least one interface must accept IPv6 traffic, and a sustained packet rate can exhaust the process, destabilize traffic, and require a device reboot.

The record

CVE
CVE-2021-1229
Published
Feb 24, 2021
Updated
Nov 8, 2024
Vendor
ClamAV
Product
Cisco NX-OS Software
Classifications
CWE-401, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 8, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco NX-OS Softwareversion=n/a

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.8Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L/E:X/RL:X/RC:X
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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