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JunosOperating system · Juniper

CVE-2020-1667

HIGH · 8.3 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 →
92/100
Remediation priority · Urgent
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
When DNS filtering is enabled on Juniper Networks Junos MX Series with one of the following cards MS-PIC, MS-MIC or MS-MPC, an incoming stream of packets processed by the Multiservices PIC Management Daemon (mspmand) process might be bypassed due to a race condition. Due to this vulnerability, mspmand process, responsible for managing "URL Filtering service", can crash, causing the Services PIC to restart. While the Services PIC is restarting, all PIC services including DNS filtering service (DNS sink holing) will be bypassed until the Services PIC completes its boot process. This issue affects Juniper Networks Junos OS: 17.3 versions prior to 17.3R3-S8; 18.3 versions prior to 18.3R3-S1; 18.4 versions prior to 18.4R3; 19.1 versions prior to 19.1R3; 19.2 versions prior to 19.2R2; 19.3 versions prior to 19.3R3. This issue does not affect Juniper Networks Junos OS 17.4, 18.1, and 18.2.

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 race condition in the Multiservices PIC Management Daemon (mspmand) on Juniper MX Series routers with MS-PIC, MS-MIC, or MS-MPC cards allows packets to bypass DNS filtering processing when the daemon crashes and triggers a Services PIC restart. During the restart window, all PIC services including DNS sinkholing are bypassed until boot completes.

MitigationUpgrade Junos OS to the specified fixed versions (17.3R3-S8, 18.3R3-S1, 18.4R3, 19.1R3, 19.2R2, or 19.3R3 or later). Evaluate disabling DNS filtering temporarily if immediate upgrade is not feasible, though this leaves DNS protection entirely disabled.

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= 18.3= 18.4= 19.1= 19.2= 19.3

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
Changed
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify device model and series
    Run 'show chassis hardware' or 'show version' to confirm the device is a Juniper MX Series router
    Affected if Device is NOT an MX Series router (different series are not affected)
  2. Verify Multiservices PIC hardware presence
    Run 'show chassis hardware' and look for MS-PIC, MS-MIC, or MS-MPC cards in the PIC slots
    Affected if No MS-PIC, MS-MIC, or MS-MPC cards are installed (the vulnerability only applies when these cards are present)
  3. Check installed Junos OS version
    Run 'show version' and identify the Junos OS version number
    Affected if Version matches 17.3, 18.3, 18.4, 19.1, 19.2, or 19.3 (exact version match to affected releases)
  4. Confirm DNS filtering is configured
    Run 'show services dns-filtering' or 'show configuration services dns-filtering' to check if DNS sinkholing or DNS filtering is enabled
    Affected if DNS filtering/sinkholing is NOT configured (the race condition only matters when DNS filtering is active)
  5. Check mspmand daemon configuration
    Run 'show system processes extensive | match mspmand' to verify the Multiservices PIC Management Daemon is running
    Affected if The mspmand daemon is not present or not applicable to your configuration

You are affected if you run an affected Junos version (17.3, 18.3, 18.4, 19.1, 19.2, or 19.3) on an MX Series router with MS-PIC/MS-MIC/MS-MPC cards and have DNS filtering enabled.

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 fixed versions (17.3R3-S8, 18.3R3-S1, 18.4R3, 19.1R3, 19.2R2, or 19.3R3 or later). Evaluate disabling DNS filtering temporarily if immediate upgrade is not feasible, though this leaves DNS protection entirely disabled.

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,800
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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-2020-1667 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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