CVE-2021-1231

SFP port switching disruption via forged LLDP packet

Published Feb 24, 2021 · Updated Nov 8, 2024

Improper access control in Cisco NX-OS System Software in ACI Mode allows attackers to disable switching on an SFP interface. The LLDP implementation incompletely validates the source of a received packet and accepts a crafted frame on the SFP interface. The attacker must reach the adjacent link, and successful exploitation interrupts traffic through that interface without affecting confidentiality or integrity.

CVSS severity4.7
Medium
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in Cisco NX-OS System Software in ACI Mode allows attackers to disable switching on an SFP interface. The LLDP implementation incompletely validates the source of a received packet and accepts a crafted frame on the SFP interface. The attacker must reach the adjacent link, and successful exploitation interrupts traffic through that interface without affecting confidentiality or integrity.

The record

CVE
CVE-2021-1231
Published
Feb 24, 2021
Updated
Nov 8, 2024
Vendor
ClamAV
Product
Cisco NX-OS System Software in ACI Mode
Classifications
CWE-346, CWE-284, T1498
Attack vector
adjacent
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 vectoradjacent
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco NX-OS System Software in ACI Modeversion=n/a

Published CVSS scores

2.9NIST National Vulnerability DatabaseAV:A/AC:M/Au:N/C:N/I:N/A:P
4.7Cisco Systems, Inc.CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L/E:X/RL:X/RC:X

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-346Origin Validation Error
CWE-284Improper Access Control
T1498Network Denial of Service

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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