Security readout for executives and security teams
Plain-English summary
This flaw can let someone with local network adjacency disrupt traffic on an SFP port of affected Cisco Nexus 9000 ACI fabric switches. It is not described as internet-routable, but it can still affect availability for connected workloads or network paths.
Executive priority
Treat as a moderate availability risk for Cisco ACI environments. It is most urgent where a disrupted SFP interface could affect production workloads, service paths, or customer-facing connectivity.
Technical view
CVE-2021-1231 is an LLDP validation flaw in Cisco Nexus 9000 Series Fabric Switches in ACI mode. Incomplete validation of received LLDP packet sources can allow an unauthenticated adjacent attacker to disable switching on an SFP interface, causing limited availability impact. The CVE maps to CWE-284.
Likely exposure
Exposure is likely limited to Cisco Nexus 9000 fabric switches running Cisco NX-OS System Software in ACI mode with reachable SFP interfaces. The attacker must be adjacent to the affected device; the source bundle does not indicate remote internet exposure.
Exploitation context
The public sources describe an unauthenticated adjacent attack path and low attack complexity. CISA KEV status is false in the supplied bundle, and no cited source here confirms active exploitation in the wild.
Researcher notes
Evidence supports adjacency-bound LLDP handling weakness with limited availability impact. The bundle does not provide fixed version details, workaround specifics, proof-of-concept status, or observed exploitation evidence, so validation should be tied directly to Cisco advisory data.
Mitigation direction
- Review Cisco advisory for affected releases and fixed software guidance.
- Prioritize remediation for ACI fabric switches carrying critical workloads.
- Reduce untrusted Layer 2 adjacency to fabric switch ports where feasible.
- Monitor affected SFP interfaces for unexpected link or switching disruption.
Validation and detection
- Inventory Nexus 9000 switches operating in ACI mode.
- Confirm NX-OS software versions against Cisco advisory guidance.
- Identify SFP interfaces exposed to adjacent or untrusted network segments.
- Review operational logs for unexplained SFP interface switching disruption.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-284: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-1231 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L2.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.7MediumVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
Source materials
- CVE List V5 sourceCVE List V5
- 20210224 Cisco Nexus 9000 Series Fabric Switches ACI Mode Link Layer Discovery Protocol Port Denial of Service VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Access Control
Improper Access Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.