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Nx OsOperating system · Cisco

CVE-2023-20168

MEDIUM · 6.5 CVSS v3.1 Published 2023-08-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
67/100
Remediation priority · Elevated
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 TACACS+ and RADIUS remote authentication for Cisco NX-OS Software could allow an unauthenticated, local attacker to cause an affected device to unexpectedly reload. This vulnerability is due to incorrect input validation when processing an authentication attempt if the directed request option is enabled for TACACS+ or RADIUS. An attacker could exploit this vulnerability by entering a crafted string at the login prompt of an affected device. A successful exploit could allow the attacker to cause the affected device to unexpectedly reload, resulting in a denial of service (DoS) condition.

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

This is a denial-of-service vulnerability in Cisco NX-OS Software affecting TACACS+ and RADIUS remote authentication when the directed request option is enabled. An unauthenticated local attacker can enter a specially crafted string at the login prompt that triggers incorrect input validation, causing the affected device to unexpectedly reload. The vulnerability stems from flawed processing of authentication attempts under specific configuration conditions.

MitigationDisable the directed request option for TACACS+ and RADIUS authentication if not operationally required, or apply the Cisco-provided software update/patch for NX-OS that addresses the input validation flaw.

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\(11\)= 10.2\(5\)all versions

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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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. Check the NX-OS version
    Execute 'show version' on the device and locate the NX-OS release line (e.g., 'Cisco NX-OS Software, Version 9.3(11)')
    Affected if The installed version matches 9.3(11), 10.2(5), or falls within any affected version range provided in the CVE advisory
  2. Verify TACACS+ authentication is configured
    Run 'show running-config | include tacacs' or 'show tacacs-server' to see if TACACS+ is enabled
    Affected if TACACS+ remote authentication is configured on the device
  3. Check if directed request is enabled for TACACS+
    Run 'show running-config all tacacs' or look for 'directed-request' under the TACACS+ server group configuration
    Affected if The 'directed request' option is enabled for TACACS+ authentication
  4. Verify RADIUS authentication is configured
    Run 'show running-config | include radius' or 'show radius-server' to see if RADIUS is enabled
    Affected if RADIUS remote authentication is configured on the device
  5. Check if directed request is enabled for RADIUS
    Run 'show running-config all radius' or look for 'directed-request' under the RADIUS server group configuration
    Affected if The 'directed request' option is enabled for RADIUS authentication

The device is affected if it runs a vulnerable NX-OS version AND has TACACS+ or RADIUS authentication configured with the directed request option enabled, because the vulnerability requires both conditions to be present for exploitation.

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

Disable the directed request option for TACACS+ and RADIUS authentication if not operationally required, or apply the Cisco-provided software update/patch for NX-OS that addresses the input validation flaw.

Recommended fix Moderate confidence

Cisco NX-OS version newer than 9.3(11) for 9.3.x train or newer than 10.2(5) for 10.2.x train (obtain exact fixed release from Cisco security advisory)

  1. 1. Verify if TACACS+ or RADIUS directed request option is enabled on the device using 'show tacacs-server' or 'show radius-server' commands
  2. 2. If directed request is enabled, consider disabling it as a temporary mitigation until upgrade can be performed using 'no tacacs-server directed-request' or 'no radius server directed-request' configuration command
  3. 3. Check Cisco's official security advisory for this CVE at sec.cloudapps.cisco.com or cisco.com to obtain the exact fixed software releases
  4. 4. Plan an upgrade to a Cisco NX-OS version newer than 9.3(11) for 9.3.x train or newer than 10.2(5) for 10.2.x train
  5. 5. Before upgrading in production, test the new version in a staging environment
  6. 6. Schedule a maintenance window and perform the upgrade following Cisco's standard NX-OS upgrade procedures
  7. 7. After upgrade, verify the vulnerability is remediated and TACACS+/RADIUS authentication still functions correctly
Caveat Ensure compatibility with your hardware platform and review Cisco NX-OS release notes for any behavioral changes between versions

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

Fix this in Nx Os Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,440
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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-2023-20168 in production — separate from our analysis above.

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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
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  • No spam, self-promotion, credentials, or personal data