Security readout for executives and security teams
Plain-English summary
CVE-2021-1586 can let an unauthenticated remote attacker crash and restart certain Cisco Nexus 9000 ACI fabric switches, causing a denial of service. Business impact is availability loss for affected ACI Multi-Pod or Multi-Site environments, not data theft based on the provided sources.
Executive priority
Treat as high priority for organizations that rely on Cisco ACI Multi-Pod or Multi-Site, especially if exposed externally. The main business risk is network fabric disruption. Scope validation should come before emergency action because the provided evidence is configuration-specific.
Technical view
The issue affects Cisco NX-OS System Software in ACI mode on Nexus 9000 fabric switches using Multi-Pod or Multi-Site configurations. Improper sanitization of TCP traffic to a specific listening port can trigger an unexpected device restart. CVSS 3.1 is 8.6 with network attack vector, low complexity, no privileges, and high availability impact.
Likely exposure
Exposure is most likely in Cisco ACI deployments using Nexus 9000 Series fabric switches with Multi-Pod or Multi-Site enabled. Risk increases where the relevant listening service is reachable on a public-facing IP address. The provided bundle does not name specific affected versions.
Exploitation context
The sources describe a remote, unauthenticated denial-of-service condition. CISA KEV status is false, and the supplied sources do not cite active exploitation. The stated impact is device restart and service disruption, with no confidentiality or integrity impact in the CVSS vector.
Researcher notes
The public bundle gives strong vulnerability mechanics but limited product-version detail. Do not assume all Nexus 9000 deployments are affected. Focus analysis on ACI mode, Multi-Pod or Multi-Site configuration, public-facing reachability, and Cisco’s advisory for authoritative remediation details.
Mitigation direction
- Review Cisco’s advisory for fixed releases and supported mitigations.
- Prioritize remediation for public-facing Multi-Pod or Multi-Site interfaces.
- Restrict external reachability to ACI Multi-Pod or Multi-Site endpoints where feasible.
- Plan maintenance windows for any required NX-OS ACI upgrades.
- Monitor fabric switches for unexpected restarts or availability instability.
Validation and detection
- Inventory Nexus 9000 switches running NX-OS in ACI mode.
- Identify deployments using ACI Multi-Pod or Multi-Site configurations.
- Compare installed software and configuration against Cisco’s advisory.
- Confirm whether relevant public-facing IPs are externally reachable.
- Review operational logs for unexplained device restarts or DoS symptoms.
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
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CWE-345: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-1586 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
- 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
- 20210825 Cisco Nexus 9000 Series Fabric Switches ACI Mode Multi-Pod and Multi-Site TCP 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.
Insufficient Verification of Data Authenticity
Insufficient Verification of Data Authenticity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.