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Nx OsOperating system · Cisco

CVE-2017-3879

MEDIUM · 5.3 CVSS v3.0 Published 2017-03-17
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
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 Denial of Service vulnerability in the remote login functionality for Cisco NX-OS Software running on Cisco Nexus 9000 Series Switches could allow an unauthenticated, remote attacker to cause a process used for login to terminate unexpectedly and the login attempt to fail. There is no impact to user traffic flowing through the device. The attacker could use either a Telnet or an SSH client for the remote login attempt. Affected Products: This vulnerability affects Cisco Nexus 9000 Series Switches that are running Cisco NX-OS Software and are configured to allow remote Telnet connections to the device. More Information: CSCuy25824. Known Affected Releases: 7.0(3)I3(1) 8.3(0)CV(0.342) 8.3(0)CV(0.345). Known Fixed Releases: 8.3(0)CV(0.362) 8.0(1) 7.0(3)IED5(0.19) 7.0(3)IED5(0) 7.0(3)I4(1) 7.0(3)I4(0.8) 7.0(3)I2(2e) 7.0(3)F1(1.22) 7.0(3)F1(1) 7.0(3)F1(0.230).

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

An unauthenticated remote attacker can cause the login process on affected Cisco Nexus 9000 Series switches to crash by sending specially crafted requests via Telnet or SSH, resulting in denial of remote administrative access. The vulnerability exists specifically in the remote login functionality and does not affect user traffic.

MitigationApply the appropriate fixed software release from Cisco (8.3(0)CV(0.362), 8.0(1), 7.0(3)I4(1), or later). If immediate patching is not possible, disable Telnet access and use SSH exclusively for remote administrative access.

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:= 7.0\(3\)i3\(0.170\)= 8.3\(0\)cv\(0.342\)= 8.3\(0\)cv\(0.345\)

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
None
Availability
Low

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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 device model
    Run 'show version' or 'show inventory' to confirm the device is a Cisco Nexus 9000 Series switch
    Affected if Device is not a Nexus 9000 Series switch, then not affected by this CVE
  2. Check NX-OS version
    Run 'show version' and look for the NX-OS software version number in the output (for example: 7.0(3)i3(0.170), 8.3(0)CV(0.342), or 8.3(0)CV(0.345))
    Affected if Installed version matches exactly 7.0(3)i3(0.170), 8.3(0)CV(0.342), or 8.3(0)CV(0.345), or falls within the vulnerable range represented by these versions
  3. Verify remote login access method
    Run 'show line' or 'show running-config | include line vty' to check if Telnet or SSH is enabled on virtual terminal lines
    Affected if Telnet or SSH access is enabled on VTY lines - the vulnerability is triggered specifically through these remote login protocols

The environment is affected if the device is a Cisco Nexus 9000 Series running NX-OS version 7.0(3)i3(0.170), 8.3(0)CV(0.342), or 8.3(0)CV(0.345) (or versions between these points) AND Telnet or SSH remote administrative access is enabled.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the appropriate fixed software release from Cisco (8.3(0)CV(0.362), 8.0(1), 7.0(3)I4(1), or later). If immediate patching is not possible, disable Telnet access and use SSH exclusively for remote administrative access.

Fix this in Nx Os Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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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-2017-3879 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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