dbcve.org
Firepower Extensible Operating SystemApplication · Cisco

CVE-2023-20234

MEDIUM · 6.0 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 →
62/100
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 the CLI of Cisco FXOS Software could allow an authenticated, local attacker to create a file or overwrite any file on the filesystem of an affected device, including system files. The vulnerability occurs because there is no validation of parameters when a specific CLI command is used. An attacker could exploit this vulnerability by authenticating to an affected device and using the command at the CLI. A successful exploit could allow the attacker to overwrite any file on the disk of the affected device, including system files. The attacker must have valid administrative credentials on the affected device to exploit this vulnerability.

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

A vulnerability in the Cisco FXOS Software CLI lacks parameter validation for a specific command, allowing an authenticated administrator to create or overwrite any file on the filesystem, including critical system files. This local privilege escalation stems from insufficient input sanitization in the CLI command parser.

MitigationApply the Cisco patch when available. Until then, strictly limit CLI access to trusted administrators only and monitor for anomalous file operations.

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
Firepower Extensible Operating SystemApplication
Affected: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
High
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:H/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 Cisco FXOS or Firepower system
    Run 'show version' or 'show inventory' in the FXOS CLI to confirm the platform is Cisco Firepower Extensible Operating System
    Affected if The system runs any version of Cisco FXOS or Firepower Software
  2. Confirm CLI access is enabled
    Check if the FXOS CLI service is accessible via console, SSH, or management interface by attempting connection or reviewing management configuration
    Affected if CLI access is enabled and reachable (this is required for the vulnerability to be exploitable)
  3. Locate the vulnerable CLI command
    Review Cisco FXOS CLI command reference documentation for commands that handle file operations (such as 'write' or file-creation commands) without proper path validation
    Affected if The vulnerable file-write command exists in the CLI and is accessible to authenticated administrators
  4. Check for anomalous file write operations
    Review system logs, audit logs, or file integrity monitoring alerts for unexpected file creation or modification events, especially in system directories
    Affected if Logs show file writes to system directories initiated through the CLI that were not performed by known trusted administrators
  5. Audit administrator accounts and CLI session logging
    Run 'show admin' or review authentication logs to list admin accounts with CLI access, and verify CLI command logging is enabled
    Affected if Multiple administrator accounts exist with CLI access and CLI command execution logging is not enabled or not retained

A user is affected if they are running any version of Cisco FXOS/Firepower with the CLI accessible to authenticated administrators, and the vulnerable file-write command is present in their CLI version.

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 the Cisco patch when available. Until then, strictly limit CLI access to trusted administrators only and monitor for anomalous file operations.

Recommended fix Moderate confidence

Contact Cisco TAC for the specific fixed FXOS release (this CVE was fixed in a subsequent FXOS release; Cisco issues per-release fixes)

  1. 1. Identify the current FXOS version by running 'show version' at the FXOS CLI
  2. 2. Contact Cisco Technical Assistance Center (TAC) or check the Cisco FXOS software download page for the latest fixed release
  3. 3. Download the fixed FXOS software version recommended by Cisco for this vulnerability
  4. 4. Follow the Cisco FXOS upgrade procedure documented in the Cisco FXOS Software Upgrade Guide
  5. 5. Verify the upgrade was successful by running 'show version' and confirming the fixed version is installed
  6. 6. Validate that the specific CLI command no longer allows unauthorized file overwriting
Caveat Review Cisco FXOS release notes for any compatibility or migration considerations before upgrading

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

Fix this in Firepower Extensible Operating System Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
25.0 hours of engineering $4,400
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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-2023-20234 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data