dbcve.org
JunosOperating system · Juniper

CVE-2020-1668

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 EX2300 Series, receipt of a stream of specific multicast packets by the layer2 interface can cause high CPU load, which could lead to traffic interruption. This issue occurs when multicast packets are received by the layer 2 interface. To check if the device has high CPU load due to this issue, the administrator can issue the following command: user@host> show chassis routing-engine Routing Engine status: ... Idle 2 percent the "Idle" value shows as low (2 % in the example above), and also the following command: user@host> show system processes summary ... PID USERNAME PRI NICE SIZE RES STATE TIME WCPU COMMAND 11639 root 52 0 283M 11296K select 12:15 44.97% eventd 11803 root 81 0 719M 239M RUN 251:12 31.98% fxpc{fxpc} the eventd and the fxpc processes might use higher WCPU percentage (respectively 44.97% and 31.98% in the above example). This issue affects Juniper Networks Junos OS on EX2300 Series: 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-S2, 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 EX2300 Series switches, receipt of specific multicast packets on a layer2 interface triggers excessive CPU utilization by the eventd and fxpc processes, potentially causing traffic interruption. The vulnerability allows a remote attacker to cause denial of service by sending a stream of crafted multicast traffic.

MitigationUpgrade Junos OS to the fixed versions specified (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, 20.1R1-S2/20.1R2 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:= 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 device model
    Run 'show chassis hardware' or 'show version' to confirm the device is an EX2300 Series switch
    Affected if Device model is EX2300 or EX2300-C Series
  2. Check Junos OS version
    Run 'show version' to obtain the installed Junos OS version
    Affected if Version begins with 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, or 20.1 (any build)
  3. Verify layer2 interface configuration
    Run 'show interfaces' or check configuration for layer2 interfaces (ge-*, xe-*) with family ethernet-switching
    Affected if Layer2 interfaces with ethernet-switching family are configured
  4. Monitor CPU utilization
    Run 'show system processes extensive' to check CPU usage of eventd and fxpc processes
    Affected if CPU utilization for eventd or fxpc processes is abnormally high (above normal baseline)
  5. Check for multicast traffic
    Run 'show interfaces statistics' on layer2 interfaces to inspect multicast packet counters
    Affected if High volume of multicast traffic is being received on layer2 interfaces

You are affected if you have an EX2300 Series switch running Junos OS versions 18.1-20.1 with layer2 interfaces receiving multicast traffic and elevated CPU on eventd or fxpc processes.

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 (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, 20.1R1-S2/20.1R2 or later).

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2020-1668 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2020-1668 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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