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JunosOperating system · Juniper

CVE-2021-0280

HIGH · 7.5 CVSS v3.1 Published 2021-07-15
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
Due to an Improper Initialization vulnerability in Juniper Networks Junos OS on PTX platforms and QFX10K Series with Paradise (PE) chipset-based line cards, ddos-protection configuration changes made from the CLI will not take effect as expected beyond the default DDoS (Distributed Denial of Service) settings in the Packet Forwarding Engine (PFE). This may cause BFD sessions to flap when a high rate of specific packets are received. Flapping of BFD sessions in turn may impact routing protocols and network stability, leading to a Denial of Service (DoS) condition. Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue affects only the following platforms with Paradise (PE) chipset-based line cards: PTX1000, PTX3000 (NextGen), PTX5000, PTX10008, PTX10016 Series and QFX10002 Series. This issue affects: Juniper Networks Junos OS 17.4 versions prior to 17.4R3-S5 on PTX Series, QFX10K Series; 18.2 versions prior to 18.2R3-S8 on PTX Series, QFX10K Series; 18.3 versions prior to 18.3R3-S5 on PTX Series, QFX10K Series; 18.4 versions prior to 18.4R2-S8 on PTX Series, QFX10K Series; 19.1 versions prior to 19.1R3-S5 on PTX Series, QFX10K Series; 19.2 versions prior to 19.2R3-S2 on PTX Series, QFX10K Series; 19.3 versions prior to 19.3R3-S2 on PTX Series, QFX10K Series; 19.4 versions prior to 19.4R3-S2 on PTX Series, QFX10K Series; 20.1 versions prior to 20.1R3 on PTX Series, QFX10K Series; 20.2 versions prior to 20.2R2-S3, 20.2R3 on PTX Series, QFX10K Series; 20.3 versions prior to 20.3R2 on PTX Series, QFX10K Series; 20.4 versions prior to 20.4R2 on PTX Series, QFX10K Series.

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

Improper Initialization vulnerability in Juniper Networks Junos OS on PTX platforms and QFX10K Series with Paradise (PE) chipset-based line cards causes ddos-protection configuration changes from CLI to not take effect beyond default settings in the Packet Forwarding Engine (PFE). This leads to BFD session flapping under high packet rates, impacting routing protocols and causing sustained DoS.

MitigationUpgrade Junos OS to a fixed version (17.4R3-S5, 18.2R3-S8, 18.3R3-S5, 18.4R2-S8, 19.1R3-S5, 19.2R3-S2, 19.3R3-S2, 19.4R3-S2, 20.1R3, 20.2R2-S3/20.2R3, 20.3R2, or 20.4R2 depending on release train). Verify ddos-protection configurations apply correctly after upgrade and monitor BFD session stability.

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:= 17.4= 18.2= 18.3= 18.4= 19.1= 19.2= 19.3= 19.4= 20.1= 20.2= 20.3= 20.4

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 hardware platform
    Run 'show chassis hardware' or 'show system hardware' to confirm the device is a PTX platform or QFX10K Series. Then check line card details for Paradise (PE) chipset using 'show chassis fpc' or 'show pic' to identify PE-based line cards.
    Affected if Device is a PTX or QFX10K with Paradise (PE) chipset-based line cards
  2. Check Junos OS version
    Run 'show version' or 'show version detail' to obtain the installed Junos OS version.
    Affected if Version matches any of: 17.4, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2, 20.3, or 20.4 (including their sub-versions)
  3. Verify ddos-protection configuration
    Run 'show configuration system ddos-protection' to review any non-default ddos-protection settings configured on the device.
    Affected if Non-default ddos-protection configuration exists beyond factory defaults
  4. Check for BFD session instability
    Run 'show bfd session extensive' or 'show bfd session' to examine BFD session state, and review system logs for BFD session flap messages, particularly under high packet rate conditions.
    Affected if BFD sessions are flapping or showing repeated state changes
  5. Confirm PFE ddos-protection settings
    Run 'show ddos protection pfe-statistics' or 'show ddos protection violations' to inspect actual Packet Forwarding Engine ddos-protection behavior versus expected CLI configuration.
    Affected if PFE-level ddos-protection settings differ from CLI configuration or show unexpected default behavior

Environment is affected if running vulnerable Junos versions on PTX or QFX10K hardware with Paradise chipset, with ddos-protection configured beyond defaults and BFD session flapping observed.

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 a fixed version (17.4R3-S5, 18.2R3-S8, 18.3R3-S5, 18.4R2-S8, 19.1R3-S5, 19.2R3-S2, 19.3R3-S2, 19.4R3-S2, 20.1R3, 20.2R2-S3/20.2R3, 20.3R2, or 20.4R2 depending on release train). Verify ddos-protection configurations apply correctly after upgrade and monitor BFD session stability.

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2021-0280 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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