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JunosOperating system · Juniper

CVE-2020-1689

MEDIUM · 6.5 CVSS v3.1 Published 2020-10-16
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
70/100
Remediation priority · Elevated
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
On Juniper Networks EX4300-MP Series, EX4600 Series and QFX5K Series deployed in a Virtual Chassis configuration, receipt of a stream of specific layer 2 frames can cause high CPU load, which could lead to traffic interruption. This issue does not occur when the device is deployed in Stand Alone configuration. The offending layer 2 frame packets can originate only from within the broadcast domain where the device is connected. This issue affects Juniper Networks Junos OS on EX4300-MP Series, EX4600 Series and QFX5K Series: 17.3 versions prior to 17.3R3-S9; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2, 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S5; 18.3 versions prior to 18.3R2-S4, 18.3R3-S3; 18.4 versions prior to 18.4R2-S5, 18.4R3-S4; 19.1 versions prior to 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R3; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2-S1, 19.4R3; 20.1 versions prior to 20.1R1-S3, 20.1R2.

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 in Juniper EX4300-MP, EX4600, and QFX5K Series switches running Junos OS in Virtual Chassis configuration allows attackers within the same broadcast domain to send specific Layer 2 frames that cause high CPU load, resulting in traffic interruption. The vulnerability does not affect Stand Alone deployments.

MitigationUpgrade Junos OS to the specified patched versions (17.3R3-S9, 17.4R2-S11/17.4R3-S3, 18.1R3-S11, 18.2R3-S5, 18.3R2-S4/18.3R3-S3, 18.4R2-S5/18.4R3-S4, 19.1R3-S2, 19.2R1-S5/19.2R3, 19.3R2-S4/19.3R3, 19.4R1-S3/19.4R2-S1/19.4R3, or 20.1R1-S3/20.1R2). Consider converting to Stand Alone configuration if upgrading is not immediately feasible.

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
JunosOperating system
Affected:= 17.3= 17.4= 18.1= 18.2= 18.3= 18.4= 19.1= 19.2= 19.3= 19.4= 20.1

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/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 the switch model
    Run 'show chassis hardware' or 'show version' and locate the hardware model in the output
    Affected if The model is EX4300-MP, EX4600, or any QFX5K series switch (QFX5100, QFX5110, QFX5120, QFX5200, QFX5210, etc.)
  2. Check the Junos OS version
    Run 'show version' and locate the Junos OS version string (e.g., 18.4R3-S4)
    Affected if The version matches 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, or 20.1 (any release within these trains)
  3. Determine if Virtual Chassis is enabled
    Run 'show virtual-chassis' or 'show virtual-chassis status'. Look for member information and VC-Mode.
    Affected if The output shows multiple member IDs or a Virtual Chassis configuration; if the output indicates 'Stand Alone' or shows only one member, the device is NOT affected

You are affected if you have an EX4300-MP, EX4600, or QFX5K switch running one of the affected Junos versions AND Virtual Chassis mode is active (not Stand Alone).

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

Upgrade Junos OS to the specified patched versions (17.3R3-S9, 17.4R2-S11/17.4R3-S3, 18.1R3-S11, 18.2R3-S5, 18.3R2-S4/18.3R3-S3, 18.4R2-S5/18.4R3-S4, 19.1R3-S2, 19.2R1-S5/19.2R3, 19.3R2-S4/19.3R3, 19.4R1-S3/19.4R2-S1/19.4R3, or 20.1R1-S3/20.1R2). Consider converting to Stand Alone configuration if upgrading is not immediately feasible.

Fix this in Junos Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2020-1689 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