dbcve.org
Nx OsOperating system · Cisco

CVE-2021-1361

CRITICAL · 9.1 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 →
100/100
Remediation priority · Urgent
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 in the implementation of an internal file management service for Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode that are running Cisco NX-OS Software could allow an unauthenticated, remote attacker to create, delete, or overwrite arbitrary files with root privileges on the device. This vulnerability exists because TCP port 9075 is incorrectly configured to listen and respond to external connection requests. An attacker could exploit this vulnerability by sending crafted TCP packets to an IP address that is configured on a local interface on TCP port 9075. A successful exploit could allow the attacker to create, delete, or overwrite arbitrary files, including sensitive files that are related to the device configuration. For example, the attacker could add a user account without the device administrator knowing.

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

This vulnerability affects Cisco Nexus 3000 and 9000 Series Switches running NX-OS in standalone mode. An internal file management service on TCP port 9075 is incorrectly exposed to external connections, allowing unauthenticated remote attackers to create, delete, or overwrite arbitrary files with root privileges by sending crafted TCP packets. Attackers can modify device configuration and add unauthorized user accounts.

MitigationApply Cisco-provided patches or firmware updates for NX-OS; alternatively, block TCP port 9075 via ACLs on all interfaces until patches can be applied.

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:= 9.3\(5\)= 9.3\(6\)

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
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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 NX-OS version
    Run 'show version' or 'show install all status' to display the running NX-OS version
    Affected if Version displayed is 9.3(5) or 9.3(6)
  2. Confirm device is in standalone mode
    Run 'show running-config | include mode' or check the system redundancy status to determine if NX-OS is operating in standalone mode rather than VPC or fabric extender mode
    Affected if Device is configured and running in standalone mode
  3. Verify TCP port 9075 is listening
    Run 'show socket connection tcp 9075' or use 'netstat -an | grep 9075' to check if the file management service is listening on port 9075
    Affected if Port 9075 shows as LISTENING or ESTABLISHED in the output
  4. Check interface access controls for port 9075
    Run 'show ip access-lists' and review applied ACLs on all interfaces (management, VLAN, physical) to determine if TCP port 9075 traffic is explicitly blocked or permitted from untrusted sources
    Affected if No ACL exists blocking TCP port 9075 on inbound interfaces, or an ACL permits traffic from external sources to port 9075
  5. Test external port accessibility
    From an untrusted network segment, attempt a TCP connection to the device management IP on port 9075 using a tool like 'nc -zv <device_ip> 9075' or 'telnet <device_ip> 9075'
    Affected if Connection to port 9075 succeeds from an untrusted host or network

The device is affected if running NX-OS version 9.3(5) or 9.3(6) in standalone mode with TCP port 9075 exposed and accessible from untrusted networks.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Cisco-provided patches or firmware updates for NX-OS; alternatively, block TCP port 9075 via ACLs on all interfaces until patches can be applied.

Recommended fix Moderate confidence

NX-OS version 9.3(7) or later (refer to Cisco security advisory for exact fixed release for your platform)

  1. 1. Identify the current Cisco NX-OS version running on the Nexus 3000 or 9000 Series Switch by running 'show version'
  2. 2. Access Cisco.com and navigate to the Cisco NX-OS Software download page or security advisories
  3. 3. Locate the security advisory for CVE-2021-1361 to obtain the fixed software release
  4. 4. Download the recommended fixed NX-OS release for your specific hardware platform (Nexus 3000 or Nexus 9000)
  5. 5. Follow the standard Cisco NX-OS upgrade procedure: upload the new software image to bootflash, set the new boot variable, and reload the device
  6. 6. After upgrade, verify that TCP port 9075 is no longer exposed externally by checking the listening services
  7. 7. Confirm the vulnerability is resolved by reviewing the fixed release notes and verifying the internal file management service is no longer externally accessible
Caveat Standard NX-OS upgrade may cause brief downtime; ensure configuration backup before upgrade; test in staging environment first

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Nx Os Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
27.0 hours of engineering $4,800
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,680.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-1361 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2021-1361 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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