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Nx OsOperating system · Cisco

CVE-2021-1230

HIGH · 7.5 CVSS v3.1 Published 2021-02-24
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A vulnerability with the Border Gateway Protocol (BGP) for Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, remote attacker to cause a routing process to crash, which could lead to a denial of service (DoS) condition. This vulnerability is due to an issue with the installation of routes upon receipt of a BGP update. An attacker could exploit this vulnerability by sending a crafted BGP update to an affected device. A successful exploit could allow the attacker to cause the routing process to crash, which could cause the device to reload. This vulnerability applies to both Internal BGP (IBGP) and External BGP (EBGP). Note: The Cisco implementation of BGP accepts incoming BGP traffic from explicitly configured peers only. To exploit this vulnerability, an attacker would need to send a specific BGP update message over an established TCP connection that appears to come from a trusted BGP peer.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

CVE-2021-1230 is a BGP route installation vulnerability in Cisco Nexus 9000 Series Fabric Switches running in ACI mode. An unauthenticated remote attacker can send a crafted BGP update message over an established TCP connection from a trusted BGP peer, causing the routing process to crash and forcing the device to reload. The vulnerability affects both IBGP and EBGP configurations.

MitigationApply Cisco security patches for affected Nexus 9000 Series devices and implement additional BGP route validation and filtering controls to reject malformed BGP updates.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Nx OsOperating system
Affected:= 12.0\(1m\)= 12.0\(1n\)= 12.0\(1o\)= 12.0\(1p\)= 12.0\(1q\)= 12.0\(1r\)= 12.0\(2f\)= 12.0\(2g\)= 12.0\(2h\)= 12.0\(2l\)= 12.0\(2m\)= 12.0\(2n\)

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the device model
    Run 'show version' or 'show inventory' to confirm the hardware is Cisco Nexus 9000 Series Fabric Switch
    Affected if Device is not a Nexus 9000 Series model, then not affected
  2. Verify the ACI mode deployment
    Run 'show system mode' or 'show fabric mode' to confirm the device is running in ACI mode
    Affected if Device is running in standalone NX-OS mode rather than ACI mode, then not affected
  3. Check the NX-OS version
    Run 'show version' and compare the installed version against the affected list: 12.0(1m), 12.0(1n), 12.0(1o), 12.0(1p), 12.0(1q), 12.0(1r), 12.0(2f), 12.0(2g), 12.0(2h), 12.0(2l), 12.0(2m), 12.0(2n)
    Affected if Installed version matches one of these specific versions, then potentially affected
  4. Confirm BGP is enabled
    Run 'show bgp summary' or 'show ip bgp summary' to verify BGP routing process is configured and active
    Affected if BGP is not configured or not running, then not vulnerable because the attack requires an established BGP session

The environment is affected if the device is a Nexus 9000 Series in ACI mode, runs a matched affected NX-OS version (12.0(1m) through 12.0(2n)), and has BGP enabled with an active peering session.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Cisco security patches for affected Nexus 9000 Series devices and implement additional BGP route validation and filtering controls to reject malformed BGP updates.

Fix this in Nx Os Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-1230 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data