CVE-2021-1523

mediumpriority · track · 34EPSS 0.013 · 71 %ileEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

1.33% (71st) EPSS

CVSS 5 · medium

Is it mine?

63 products

Check your exposure

Who says so?

3 sources

cnnvd · enisa_euvd · cisco_csaf

EPSS · scored 2026-10-22

A vulnerability in Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) Mode could allow an unauthenticated, remote attacker to cause a queue wedge on a leaf switch, which could result in critical control plane traffic to the device being dropped. This could result in one or more leaf switches being removed from the fabric. This vulnerability is due to mishandling of ingress TCP traffic to a specific port. An attacker could exploit this vulnerability by sending a stream of TCP packets to a specific port on a Switched Virtual Interface (SVI) configured on the device. A successful exploit could allow the attacker to cause a specific packet queue to queue network buffers but never process them, leading to an eventual queue wedge. This could cause control plane traffic to be dropped, resulting in a denial of service (DoS) condition where the leaf switches are unavailable. Note: This vulnerability requires a manual intervention to power-cycle the device to recover.

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

FixedCisco NX-OS System Software in ACI Mode 13.2(1l) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(1m) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(2l) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(2o) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(3i) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(3j) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(3n) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(3o) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(3r) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(3s) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(41d) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(4d) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(4e) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(5d) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(5e) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(5f) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(6i) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(7f) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(7k) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(8d) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(9b) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(9f) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 13.2(9h) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.0(1h) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.0(2c) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.0(3c) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.0(3d) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(1i) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(1j) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(1k) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(1l) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(2g) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(2m) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(2o) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(2s) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(2u) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(2w) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.1(2x) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(1i) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(1j) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(1l) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(2e) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(2f) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(2g) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(3j) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(3l) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(3n) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(3q) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(4i) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(4k) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(4o) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(4p) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(5k) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(5l) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(5n) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(6d) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(6g) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(6h) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(6l) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco NX-OS System Software in ACI Mode 14.2(6o) when installed on Cisco Nexus 9000 Series Switchescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com

cvss

Technical severity, 0–10. One row per scoring source.

8.6

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 5–8.6

v2.05mediumAV:N/AC:L/Au:N/C:N/I:N/A:Pprimary · NVD / NIST USexploitability 10 · impact 2.9

v3.18.6highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 4

v3.18.6highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:Hsecondary · ENISA EU

v3.18.6highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:Hsecondary · psirt@cisco.com USexploitability 3.9 · impact 4

v3.17.9highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:Usecondary · CVSS-BT (t0sche)

v3.18.6highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:Hsecondary · Cisco PSIRT US

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: yes · Technical Impact: partialcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-772USprimary

affected products (63)

Products and version ranges known to be affected.

showing 20 of 63

advisories (1)

Vendor and ecosystem advisories describing this.

cisco-sa-n9kaci-queue-wedge-cLDDEfKFCisco Nexus 9000 Series Fabric Switches ACI Mode Queue Wedge Denial of Service Vulnerability2021-08-25csaf · cisco_csafUS
A vulnerability in Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) Mode could allow an unauthenticated, remote attacker to cause a queue wedge on a leaf switch, which could result in critical control plane traffic to the device being dropped. This could result in one or more leaf switches being removed from the fabric. This vulnerability is due to mishandling of ingress TCP traffic to a specific port. An attacker could exploit this vulnerability by sending a stream of TCP packets to a specific port on a Switched Virtual Interface (SVI) configured on the device. A successful exploit could allow the attacker to cause a specific packet queue to queue network buffers but never process them, leading to an eventual queue wedge. This could cause control plane traffic to be dropped, resulting in a denial of service (DoS) condition where the leaf switches are unavailable. Note: This vulnerability requires a manual intervention to power-cycle the device to recover. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is part of the August 2021 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: August 2021 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication ["https://sec.cloudapps.cisco.com/security/center/viewErp.x?alertId=ERP-74640"].

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd cisco_csaf NVD CVE.org MITRE

published 2021-08-25modified 2026-06-17

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+1012 more

references (5)

External citations — patches, advisories, analysis.

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