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JunosOperating system · Juniper

CVE-2020-1687

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 (Ethernet VPN) EVPN-(Virtual Extensible LAN) VXLAN configuration, receipt of a stream of specific VXLAN encapsulated layer 2 frames can cause high CPU load, which could lead to network protocol operation issue and traffic interruption. This issue affects devices that are configured as a Layer 2 or Layer 3 gateway of an EVPN-VXLAN deployment. The offending layer 2 frames that cause the issue originate from a different access switch that get encapsulated within the same EVPN-VXLAN domain. 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 19.1R2-S2, 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R2-S1, 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

On Juniper Networks EX4300-MP, EX4600, and QFX5K Series switches configured as EVPN-VXLAN Layer 2 or Layer 3 gateways, receipt of specific VXLAN encapsulated layer 2 frames from other access switches within the same EVPN-VXLAN domain triggers a denial of service condition causing elevated CPU load. This high CPU utilization disrupts network protocol operations and leads to traffic interruption.

MitigationUpgrade Junos OS to the fixed versions specified in the advisory (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, 19.1R2-S2/19.1R3-S2, 19.2R1-S5/19.2R2-S1/19.2R3, 19.3R2-S4/19.3R3, 19.4R1-S3/19.4R2-S1/19.4R3, or 20.1R1-S3/20.1R2 or later).

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 switch model
    Run 'show chassis hardware' or check the physical device labeling to confirm the model is EX4300-MP, EX4600, or a QFX5K Series switch (QFX5100, QFX5110, QFX5120, QFX5200, QFX5210, QFX5110-32Q, QFX5110-48S)
    Affected if The device is NOT one of these models - the vulnerability does not apply
  2. Check Junos OS version
    Run 'show version' to obtain the installed Junos version
    Affected if The installed version matches one of the affected versions listed: 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 branches)
  3. Verify EVPN-VXLAN configuration
    Run 'show configuration | display set | match evpn' and 'show configuration | display set | match vxlan' to check for EVPN and VXLAN configuration statements
    Affected if EVPN-VXLAN is configured - the device is acting as an EVPN-VXLAN gateway
  4. Confirm gateway role
    Run 'show evpn instance' and 'show vlans' or 'show bridge domains' to determine if the device is operating as a Layer 2 gateway, Layer 3 gateway (IRB interface configured), or both
    Affected if The device is configured as an EVPN-VXLAN Layer 2 gateway or Layer 3 gateway (IRB interface present in EVPN instance)

A user is affected if they have an EX4300-MP, EX4600, or QFX5K Series switch running a listed Junos version AND configured as an EVPN-VXLAN Layer 2 or Layer 3 gateway receiving VXLAN traffic from other switches in the same EVPN-VXLAN domain.

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 fixed versions specified in the advisory (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, 19.1R2-S2/19.1R3-S2, 19.2R1-S5/19.2R2-S1/19.2R3, 19.3R2-S4/19.3R3, 19.4R1-S3/19.4R2-S1/19.4R3, or 20.1R1-S3/20.1R2 or later).

Fix this in Junos Scoped from the published advisory
  • Consultation6.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
26.0 hours of engineering $4,560
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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-2020-1687 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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