CVE-2021-1229· NVD / CVE Program· CNA cisco

Cisco NX-OS Software ICMP Version 6 Memory Leak Denial of Service Vulnerability

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.

MediumCVSS 5.3 · v3.1—No exploit No fix recorded

BDU:2021-01081

Published: Feb 24, 2021
Updated: Jun 16, 2026
EPSS: 1.4% · 72th percentile
CWE: CWE-401

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Action score

Monitor

Low priority for now.

CVSS: 21 / 40 · 5.3 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 1.4%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 5.3
CNA · cisco: 5.8; 0.5 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

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Affected systems

Vendor	Product	CPE
cisco	nx-os	cpe:2.3:o:cisco:nx-os
cisco	nexus 1000 virtual edge for vmware vsphere	cpe:2.3:h:cisco:nexus_1000_virtual_edge_for_vmware_vsphere
cisco	nexus 1000v switch for microsoft hyper-v	cpe:2.3:h:cisco:nexus_1000v_switch_for_microsoft_hyper-v
cisco	nexus 1000v switch for vmware vsphere	cpe:2.3:h:cisco:nexus_1000v_switch_for_vmware_vsphere
cisco	mds 9148s	cpe:2.3:h:cisco:mds_9148s
cisco	mds 9250i	cpe:2.3:h:cisco:mds_9250i
cisco	mds 9706	cpe:2.3:h:cisco:mds_9706
cisco	mds 9710	cpe:2.3:h:cisco:mds_9710
cisco	nexus 3048	cpe:2.3:h:cisco:nexus_3048
cisco	nexus 31108pv-v	cpe:2.3:h:cisco:nexus_31108pv-v
cisco	nexus 31108tc-v	cpe:2.3:h:cisco:nexus_31108tc-v
cisco	nexus 31128pq	cpe:2.3:h:cisco:nexus_31128pq

and 74 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

cisco nx-os15.1(2.31)
cisco nx-os5.2(1)sv5(1.3a)
cisco nx-os8.4(3.53)

Versions reported by the vendor

Affected version ranges reported by the assigning authority (cisco). Independent of NVD's CPE analysis and usually ahead of it.

Cisco Cisco NX-OS Software
- n/aaffected

Same product

cisco: all records

Other highest-scoring records for the same primary product.

CVE-2024-20399Cisco NX-OS Software CLI Command Injection VulnerabilityKEV
57Plan
CVE-2018-0301A vulnerability in the NX-API feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to craft a packet to the manag
44Plan
CVE-2016-1453Buffer overflow in the Overlay Transport Virtualization (OTV) GRE feature in Cisco NX-OS 5.0 through 7.3 on Nexus 7000 and 7700 devices allo
41Plan
CVE-2018-0310A vulnerability in the Cisco Fabric Services component of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, remot
40Plan
CVE-2022-20650Cisco NX-OS Software NX-API Command Injection Vulnerability
39Monitor
CVE-2016-1341Cisco NX-OS 7.0(1)N1(1), 7.0(1)N1(3), and 7.0(4)N1(1) on Nexus 2000 Fabric Extender devices has a blank root password, which allows local us
39Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).