dbcve.org
Nx OsOperating system · Cisco

CVE-2019-1967

HIGH · 7.5 CVSS v3.1 Published 2019-08-30
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
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 vulnerability in the Network Time Protocol (NTP) feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to excessive use of system resources when the affected device is logging a drop action for received MODE_PRIVATE (Mode 7) NTP packets. An attacker could exploit this vulnerability by flooding the device with a steady stream of Mode 7 NTP packets. A successful exploit could allow the attacker to cause high CPU and memory usage on the affected device, which could cause internal system processes to restart or cause the affected device to unexpectedly reload. Note: The NTP feature is enabled by default.

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 denial-of-service vulnerability exists in Cisco NX-OS NTP feature where excessive logging of dropped MODE_PRIVATE (Mode 7) NTP packets consumes system resources. An unauthenticated remote attacker can flood the device with Mode 7 NTP packets, causing high CPU/memory usage that triggers internal process restarts or device reloads.

MitigationDisable NTP if not required, or apply the Cisco NX-OS security patch when available. Consider implementing ACLs to filter unsolicited NTP traffic at network edges.

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:= 6.2= 7.3= 8.1= 8.2= 8.3= 6.0\(2\)a8\(9.7\)= 6.0\(2\)u6= 7.0\(3\)i= 9.2= 9.2\(1\)= 6.0\(2\)a8= 7.0\(3\)i7

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
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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. Identify NX-OS version
    Run 'show version' or 'show version | include NXOS' to display the installed NX-OS version
    Affected if The displayed version matches or falls within the affected ranges: 6.0(2)a8, 6.0(2)a8(9.7), 6.0(2)u6, 6.2, 7.0(3)i, 7.0(3)i7, 7.3, 8.1, 8.2, 8.3, 9.2, 9.2(1)
  2. Verify NTP is enabled
    Run 'show running-config | include ntp' or 'show ntp service' to check if NTP is configured and active on the device
    Affected if NTP is enabled and running on the device (the vulnerability only affects systems with NTP actively processing packets)
  3. Confirm NTP server configuration
    Run 'show ntp associations' or 'show running-config | section ntp' to list configured NTP peers or servers
    Affected if Any NTP server or peer configuration exists, indicating the device is acting as an NTP client or accepting NTP queries
  4. Inspect logs for Mode 7 packet drops
    Run 'show logging | include mode' or 'show logging | include NTP' to search log buffers for messages related to Mode 7 or private mode NTP packets being dropped
    Affected if Logs show frequent messages about dropped Mode 7 or MODE_PRIVATE NTP packets, indicating the condition is being triggered

A device is affected if it runs an affected NX-OS version AND has NTP enabled/active, making it vulnerable to resource exhaustion from malicious Mode 7 NTP packets.

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

Disable NTP if not required, or apply the Cisco NX-OS security patch when available. Consider implementing ACLs to filter unsolicited NTP traffic at network edges.

Fix this in Nx Os Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2019-1967 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