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Nx OsOperating system · Cisco

CVE-2018-0294

MEDIUM · 6.7 CVSS v3.0 Published 2018-06-20
Fix available
A fix is available. Upgrade to 2.0.1.159 / 2.1.1.86 or later.
See remediation →
69/100
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 write-erase feature of Cisco FXOS Software and Cisco NX-OS Software could allow an authenticated, local attacker to configure an unauthorized administrator account for an affected device. The vulnerability exists because the affected software does not properly delete sensitive files when certain CLI commands are used to clear the device configuration and reload a device. An attacker could exploit this vulnerability by logging into an affected device as an administrative user and configuring an unauthorized account for the device. The account would not require a password for authentication and would be accessible only via a Secure Shell (SSH) connection to the device. A successful exploit could allow the attacker to configure an unauthorized account that has administrative privileges, does not require a password for authentication, and does not appear in the running configuration or the audit logs for the affected device. This vulnerability affects Firepower 4100 Series Next-Generation Firewalls, Firepower 9300 Security Appliance, Nexus 1000V Series Switches, Nexus 1100 Series Cloud Services Platforms, Nexus 2000 Series Fabric Extenders, Nexus 3500 Platform Switches, Nexus 4000 Series Switches, Nexus 5500 Platform Switches, Nexus 5600 Platform Switches, Nexus 6000 Series Switches, UCS 6100 Series Fabric Interconnects, UCS 6200 Series Fabric Interconnects, UCS 6300 Series Fabric Interconnects. Cisco Bug IDs: CSCvd13993, CSCvd34845, CSCvd34857, CSCvd34862, CSCvd34879, CSCve35753.

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 write-erase feature of Cisco FXOS and NX-OS software fails to properly delete sensitive files when the CLI is used to clear device configuration and reload. An authenticated local attacker with administrative access can exploit this to create a hidden, passwordless administrator account accessible via SSH that does not appear in the running configuration or audit logs.

MitigationApply Cisco patches for CSCvd13993 and related bug IDs. Manually audit existing devices for unauthorized accounts and verify write-erase functionality after patching. Consider network segmentation and enhanced monitoring until patches are 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:= 7.3\(2\)n1\(0.354\)= 5.2\(1\)sv3\(1.10\)= 8.8\(3.5\)s0= 7.0\(3\)i2\(4a\)= 4.1\(2\)e1\(1a\)
Firepower Extensible Operating SystemOperating system
Affected:>= 2.1.1, < 2.1.1.86>= 2.2, < 2.2.2.17
FxosOperating system
Affected:>= 1.1, < 2.0.1.159

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
High
Integrity
High
Availability
High

CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:H/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 the NX-OS or FXOS software version
    Run 'show version' or 'show version installed' on the device CLI to obtain the exact software version
    Affected if The installed version matches one of the affected versions: NX-OS 7.3(2)n1(0.354), 5.2(1)sv3(1.10), 8.8(3.5)s0, 7.0(3)i2(4a), or 4.1(2)e1(1a); FXOS/Firepower 2.1.1 through 2.1.1.85; FXOS/Firepower 2.2.0 through 2.2.2.16; or FXOS 1.1.0 through 2.0.1.158
  2. Check for hidden local administrator accounts
    Use 'show running-config all' and 'show startup-config' to compare all accounts; also use 'show privilege' and review 'show users' output. For deeper inspection, access the underlying file system via 'run bash' or check /etc/passwd equivalents if available
    Affected if There are administrator accounts present in the system that do not appear in the running configuration or startup configuration
  3. Review authentication logs for anomalous SSH activity
    Check 'show logging' output and any external syslog servers for SSH authentication events, particularly successful logins to accounts not defined in the configuration
    Affected if SSH authentication records exist for administrator accounts that are not defined in the device configuration
  4. Verify if write-erase was recently performed
    Check system logs, boot timestamps, and configuration archive for evidence of write-erase and reload operations using 'show logging' and 'show boot'
    Affected if The device has undergone a write-erase operation followed by a reload, and the software version falls within the affected range

The device is likely affected if it runs a vulnerable NX-OS or FXOS version and shows evidence of write-erase usage or contains undocumented administrator accounts accessible via SSH.

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 2.0.1.159 / 2.1.1.86 / 2.2.2.17 or later
Fixed in 2.0.1.1592.1.1.862.2.2.17
Interim mitigation

Apply Cisco patches for CSCvd13993 and related bug IDs. Manually audit existing devices for unauthorized accounts and verify write-erase functionality after patching. Consider network segmentation and enhanced monitoring until patches are applied.

Fix this in Nx Os Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2018-0294 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