Security readout for executives and security teams
Plain-English summary
This flaw can let a remote, unauthenticated actor crash routing on Cisco Nexus 9000 ACI fabric switches by abusing BGP route processing. Business impact is availability: affected switches may reload, disrupting data center fabric connectivity. The attack is constrained because traffic must appear to come from a configured trusted BGP peer.
Executive priority
Treat as high priority for data center fabrics using Cisco Nexus 9000 ACI mode with BGP. The likely business risk is outage, not data theft. Prioritize environments where BGP peers are numerous, externally connected, or not tightly governed.
Technical view
CVE-2021-1230 affects Cisco NX-OS System Software in ACI mode on Nexus 9000 Series Fabric Switches. A crafted BGP update can trigger a route installation issue, crash the routing process, and potentially reload the device. It applies to both IBGP and EBGP. CVSS v3.1 is 8.6, with high availability impact.
Likely exposure
Exposure is limited to environments running Cisco Nexus 9000 Series Fabric Switches in ACI mode with configured BGP peers. The Cisco implementation accepts BGP traffic only from explicitly configured peers, so practical exposure depends on trusted peer control and adjacency hygiene.
Exploitation context
The source bundle does not indicate known active exploitation or KEV listing. Exploitation requires a specific BGP update over an established TCP connection that appears to come from a trusted configured BGP peer.
Researcher notes
The key constraint is peer trust: Cisco states incoming BGP traffic is accepted only from explicitly configured peers. Analysis should focus on affected ACI-mode deployments, BGP adjacency boundaries, and whether route processing crashes or reloads are observable in operational logs.
Mitigation direction
- Review Cisco’s advisory for fixed software and deployment-specific guidance.
- Inventory Nexus 9000 ACI-mode switches and identify BGP-enabled fabrics.
- Remove stale, unnecessary, or unmanaged BGP peer relationships.
- Restrict BGP adjacency paths to trusted network zones where operationally possible.
- Monitor affected fabrics for routing process crashes and unexpected device reloads.
Validation and detection
- Confirm whether any Nexus 9000 switches run NX-OS in ACI mode.
- Enumerate IBGP and EBGP peers on affected ACI fabrics.
- Check maintenance records against Cisco advisory guidance for this CVE.
- Review logs for routing process crashes or unexplained switch reloads.
- Validate that configured BGP peers are expected, managed, and documented.
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
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ATT&CK lookup starting points
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CWE-233: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-1230 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 8.6 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
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:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.6HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20210224 Cisco Nexus 9000 Series Fabric Switches ACI Mode BGP Route Installation 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 Handling of Parameters
Improper Handling of Parameters represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.