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Data Center Network ManagerApplication · Cisco

CVE-2021-1255

MEDIUM · 5.4 CVSS v3.1 Published 2021-01-20
Fix available
A fix is available. Upgrade to 11.4 or later.
See remediation →
60/100
Remediation priority · Elevated
Remotely reachable 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
Multiple vulnerabilities in the REST API endpoint of Cisco Data Center Network Manager (DCNM) could allow an authenticated, remote attacker to view, modify, and delete data without proper authorization. For more information about these vulnerabilities, see the Details section of this advisory.

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 · moderate confidence

Multiple vulnerabilities in the REST API of Cisco Data Center Network Manager allow authenticated attackers to perform unauthorized CRUD operations (view, modify, delete) on data without proper authorization checks - consistent with Insecure Direct Object Reference (IDOR) or broken access control flaws in the API layer.

MitigationApply the vendor patch from Cisco for CVE-2021-1255; if unavailable, implement role-based access control (RBAC) and object-level authorization validation in the REST API endpoints, and restrict API access to essential personnel only.

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
Data Center Network ManagerApplication
Affected:< 11.4\(1\)

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

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

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 Cisco DCNM version
    Locate the installed version of Cisco Data Center Network Manager. This is typically accessible via the DCNM web interface (Help > About), the DCNM CLI, or the API endpoint /fm/fmRest/about. Compare the version number to the affected range: versions prior to 11.4(1) are vulnerable.
    Affected if The installed version is below 11.4(1)
  2. Confirm REST API is accessible
    Verify that the DCNM REST API endpoints are reachable. Test connectivity to common DCNM API paths such as /fm/fmRest or /app/api/v1. Check network configuration to determine if API ports (default 443 for HTTPS) are open and accessible.
    Affected if The REST API is accessible over the network to authenticated users
  3. Check RBAC configuration
    Review the role-based access control settings in DCNM. Access the administration or security settings via the web UI or API to enumerate user roles and their assigned permissions. Look for roles that grant broad or excessive privileges.
    Affected if RBAC is not properly configured or users have overly permissive role assignments
  4. Audit API endpoint authorization
    Use an authenticated API client to make CRUD requests to various REST API endpoints (e.g., /fm/fmRest/devices, /fm/fmRest/fabric). Observe whether the API enforces proper object-level authorization or allows access to resources outside the user's assigned scope.
    Affected if An authenticated user can access, modify, or delete resources they should not have authorization to touch

A user is affected if their Cisco DCNM installation is version 11.3.x or earlier and the REST API is accessible to authenticated users without proper object-level authorization enforcement.

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
Upgrade available Upgrade to 11.4 or later
Fixed in 11.4
Interim mitigation

Apply the vendor patch from Cisco for CVE-2021-1255; if unavailable, implement role-based access control (RBAC) and object-level authorization validation in the REST API endpoints, and restrict API access to essential personnel only.

Fix this in Data Center Network Manager Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,380
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,808.

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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-2021-1255 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