Nx OsOperating system · Cisco
CVE-2017-3878
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 · uneditedA Denial of Service vulnerability in the Telnet remote login functionality of Cisco NX-OS Software running on Cisco Nexus 9000 Series Switches could allow an unauthenticated, remote attacker to cause a Telnet process used for login to terminate unexpectedly and the login attempt to fail. There is no impact to user traffic flowing through the device. 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: CSCux46778. Known Affected Releases: 7.0(3)I3(0.170). Known Fixed Releases: 7.0(3)I3(1) 7.0(3)I3(0.257) 7.0(3)I3(0.255) 7.0(3)I2(2e) 7.0(3)F1(1.22) 7.0(3)F1(1).
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 confidenceA Denial of Service vulnerability exists in the Telnet remote login functionality of Cisco NX-OS Software on Nexus 9000 Series Switches. An unauthenticated, remote attacker can send malicious traffic during a Telnet login attempt to cause the Telnet process to terminate unexpectedly, resulting in login failure. User traffic through the device is unaffected.
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
= 7.0\(3\)i3\(0.170\)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 checksWork through these to decide whether this CVE applies to you.
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Identify device hardware and softwareRun 'show version' or 'show inventory' on the Cisco Nexus 9000 switch to confirm hardware model and NX-OS versionAffected if The device is a Cisco Nexus 9000 Series Switch running NX-OS version 7.0(3)i3(0.170)
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Verify exact NX-OS versionExecute 'show version | include version' or check the 'NXOS: version' line in the show version outputAffected if The NX-OS version is exactly 7.0(3)i3(0.170)
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Confirm Telnet is enabledRun 'show telnet server' or 'show running-config | include telnet' to check if Telnet remote login functionality is configuredAffected if Telnet server or Telnet login is enabled on the device
You are affected only if you are running a Nexus 9000 Series Switch with NX-OS version 7.0(3)i3(0.170) and Telnet remote access is enabled
Generated from the published advisory. Verify against your own configuration.
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 dataUpgrade Cisco NX-OS to a fixed release (7.0(3)I3(1), 7.0(3)I3(0.257), 7.0(3)I3(0.255), 7.0(3)I2(2e), 7.0(3)F1(1.22), or 7.0(3)F1(1)). Alternatively, disable Telnet and use SSH for remote access as a compensating control.
Fix this in Nx Os
Scoped from the published advisory
- Consultation4.0 h
- Implementation6.0 h
- Testing2.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-3878 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2017-3878 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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