CVE-2021-1586Network attack vector

Device restart via unsanitized TCP traffic

Published Aug 25, 2021 · Updated Nov 7, 2024

Denial of service in Cisco NX-OS System Software in ACI Mode allows remote attackers to restart affected switches with crafted TCP data. A public-facing IPN or ISN interface accepts TCP traffic on a specific port without properly sanitizing the supplied data, allowing the device to restart. Exposure requires a Nexus 9000 switch in ACI mode with Multi-Pod or Multi-Site configured and an IP address on the spine interface; a successful attack interrupts traffic during the restart.

CVSS severity8.6
High
EPSS probability2.45%
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 System Software in ACI Mode allows remote attackers to restart affected switches with crafted TCP data. A public-facing IPN or ISN interface accepts TCP traffic on a specific port without properly sanitizing the supplied data, allowing the device to restart. Exposure requires a Nexus 9000 switch in ACI mode with Multi-Pod or Multi-Site configured and an IP address on the spine interface; a successful attack interrupts traffic during the restart.

The record

CVE
CVE-2021-1586
Published
Aug 25, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco NX-OS System Software in ACI Mode
Classifications
CWE-345, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 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 System Software in ACI Modeversion=n/a

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
8.6CiscoCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-345Insufficient Verification of Data Authenticity
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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