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JunosOperating system · Juniper

CVE-2020-1639

HIGH · 7.5 CVSS v3.1 Published 2020-04-08
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
When an attacker sends a specific crafted Ethernet Operation, Administration, and Maintenance (Ethernet OAM) packet to a target device, it may improperly handle the incoming malformed data and fail to sanitize this incoming data resulting in an overflow condition. This overflow condition in Juniper Networks Junos OS allows an attacker to cause a Denial of Service (DoS) condition by coring the CFM daemon. Continued receipt of these packets may cause an extended Denial of Service condition. This issue affects: Juniper Networks Junos OS 12.3 versions prior to 12.3R12-S15; 12.3X48 versions prior to 12.3X48-D95 on SRX Series; 14.1X50 versions prior to 14.1X50-D145; 14.1X53 versions prior to 14.1X53-D47; 15.1 versions prior to 15.1R2; 15.1X49 versions prior to 15.1X49-D170 on SRX Series; 15.1X53 versions prior to 15.1X53-D67.

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

This is a buffer overflow vulnerability in the CFM (Connectivity Fault Management) daemon of Juniper Junos OS. When the device receives a specially crafted Ethernet OAM packet, the daemon fails to properly sanitize the malformed input, causing an overflow condition that results in the daemon coring (crashing). Repeated receipt of these packets creates a sustained DoS condition.

MitigationApply the vendor-supplied Junos OS patches to the fixed versions listed (12.3R12-S15, 12.3X48-D95, 14.1X50-D145, etc.) or implement network-level filtering to block unauthorized Ethernet OAM traffic at perimeter devices.

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:= 12.3= 12.3x48= 14.1x50= 14.1x53= 15.1= 15.1x49= 15.1x53

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 Junos OS version
    Run 'show version' or 'show version detail' on the Juniper device CLI to retrieve the installed Junos OS version number
    Affected if The version matches one of the affected ranges: 12.3, 12.3X48, 14.1X50, 14.1X53, 15.1, 15.1X49, or 15.1X53 (specific build numbers may vary within these branches)
  2. Confirm CFM daemon is active
    Run 'show cfm statistics' or 'show protocols oam' to verify the Connectivity Fault Management daemon is running on the device
    Affected if CFM/OAM functionality is enabled and the daemon is actively processing Ethernet OAM packets
  3. Check CFM interface configuration
    Run 'show cfm interface' to list all interfaces where CFM is configured
    Affected if Any interface has CFM MEP (Maintenance End Point) or MIP (Maintenance Intermediate Point) configured
  4. Verify OAM protocol reception
    Inspect logs with 'show log messages | match CFM' or monitor traffic on interfaces configured for CFM to confirm the device is receiving Ethernet OAM packets
    Affected if The device is processing incoming Ethernet OAM traffic on CFM-enabled interfaces

A user is affected if the device runs a Junos OS version within the affected ranges AND has CFM (Connectivity Fault Management) enabled, making it vulnerable to the buffer overflow when receiving malformed Ethernet OAM 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

Apply the vendor-supplied Junos OS patches to the fixed versions listed (12.3R12-S15, 12.3X48-D95, 14.1X50-D145, etc.) or implement network-level filtering to block unauthorized Ethernet OAM traffic at perimeter devices.

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
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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-2020-1639 in production — separate from our analysis above.

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