How severe is CVE-2021-1231?

CVE-2021-1231 has a CVSS 3.x base score of 4.7, rated medium severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2021-1231 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-1231?

CVE-2021-1231 primarily affects Cisco Nx-os. In total, 164 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-1231?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-1231 published?

CVE-2021-1231 was published on 2021-02-24 and last updated on 2026-06-17.

CVE-2021-1231

CVE-2021-1231 is a medium-severity vulnerability in Cisco Nx-os with a CVSS 3.x base score of 4.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-346.

Key facts

Severity: Medium (CVSS 3.x base score 4.7)
CVSS v2: 2.9
EPSS exploit prediction: 0% (15th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-346
Affected product: Cisco Nx-os
Published: 2021-02-24
Last modified: 2026-06-17

Description

A vulnerability in the Link Layer Discovery Protocol (LLDP) for Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, adjacent attacker to disable switching on a small form-factor pluggable (SFP) interface. This vulnerability is due to incomplete validation of the source of a received LLDP packet. An attacker could exploit this vulnerability by sending a crafted LLDP packet on an SFP interface to an affected device. A successful exploit could allow the attacker to disable switching on the SFP interface, which could disrupt network traffic.

Frequently asked questions

What is CVE-2021-1231?: A vulnerability in the Link Layer Discovery Protocol (LLDP) for Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, adjacent attacker to disable switching on a small form-factor pluggable (SFP) interface. This vulnerability is due to incomplete validation of the source of a received LLDP packet. An attacker could exploit this vulnerability by sending a crafted LLDP packet on an SFP interface to an affected device. A successful exploit could allow the attacker to disable switching on the SFP interface, which could disrupt network traffic.
How severe is CVE-2021-1231?: CVE-2021-1231 has a CVSS 3.x base score of 4.7, rated medium severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2021-1231 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-1231?: CVE-2021-1231 primarily affects Cisco Nx-os. In total, 164 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-1231?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-1231 published?: CVE-2021-1231 was published on 2021-02-24 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apic-lldap-dos-WerV9CFj

Affected products (164)

cpe:2.3:o:cisco:nx-os:11.0\(1b\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(1c\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(1d\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(1e\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(2j\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(2m\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(3f\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(3i\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(3k\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(3n\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(3o\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(4g\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(4h\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(4o\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.0\(4q\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(1j\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(1o\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(1r\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(1s\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(2h\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(2i\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(3f\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(4e\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(4f\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(4g\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(4i\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(4l\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.1\(4m\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(1i\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(1k\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(1m\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(2g\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(2h\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(2i\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(2j\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(3c\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(3e\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(3h\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.2\(3m\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:11.3\(1g\):*:*:*:*:*:*:*

More vulnerabilities in Cisco Nx-os

CVE-2021-1361 — Critical (CVSS 9.8): A vulnerability in the implementation of an internal file management service for Cisco Nexus 3000 Series Switches and…
CVE-2018-0310 — Critical (CVSS 9.8): A vulnerability in the Cisco Fabric Services component of Cisco FXOS Software and Cisco NX-OS Software could allow an…
CVE-2018-0301 — Critical (CVSS 9.8): A vulnerability in the NX-API feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to craft…
CVE-2016-1453 — Critical (CVSS 9.8): Buffer overflow in the Overlay Transport Virtualization (OTV) GRE feature in Cisco NX-OS 5.0 through 7.3 on Nexus 7000…
CVE-2016-1341 — Critical (CVSS 9.8): Cisco 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,…
CVE-2015-4235 — Critical (CVSS 9.0): Cisco Application Policy Infrastructure Controller (APIC) devices with software before 1.0(3o) and 1.1 before 1.1(1j)…

All CVEs affecting Cisco Nx-os →

Other CWE-346 vulnerabilities

CVE-2026-42901 — Critical (CVSS 10.0): Origin validation error in Microsoft Entra ID allows an unauthorized attacker to elevate privileges over a network.
CVE-2026-6508 — Critical (CVSS 9.8): Origin Validation Error vulnerability in TUBITAK BILGEM Software Technologies Research Institute Liderahenk allows…
CVE-2026-2790 — Critical (CVSS 9.8): Same-origin policy bypass in the Networking: JAR component. This vulnerability was fixed in Firefox 148, Firefox ESR…
CVE-2022-50925 — Critical (CVSS 9.8): Prowise Reflect version 1.0.9 contains a remote keystroke injection vulnerability that allows attackers to send…
CVE-2025-30466 — Critical (CVSS 9.8): This issue was addressed through improved state management. This issue is fixed in Safari 18.4, iOS 18.4 and iPadOS…
CVE-2024-8487 — Critical (CVSS 9.8): A Cross-Origin Resource Sharing (CORS) vulnerability exists in modelscope/agentscope version v0.0.4. The CORS…

Browse all CWE-346 vulnerabilities →