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CVE Record

CVE-2021-0280: Junos OS: PTX Series, QFX10K Series: Upon receipt of specific packets BFD sessions might flap due to DDoS policer implementation in Packet Forwarding Engine

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.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Certain Juniper core and data-center routing platforms may not apply custom DDoS protection settings as intended. Under a high rate of specific packets, BFD sessions can flap, which can disrupt routing stability and create a denial-of-service condition.

Executive priority

Prioritize remediation on backbone, edge, and data-center fabrics where BFD instability could cause customer-visible outages or route churn. This is not a data theft issue, but it can affect service availability on critical network infrastructure.

Technical view

CVE-2021-0280 is an improper initialization flaw in Junos OS PFE DDoS policer handling on PTX and QFX10K/QFX10002 platforms using Paradise chipset line cards. CLI ddos-protection changes may not take effect beyond defaults, allowing specific high-rate packet traffic to trigger BFD flaps and availability impact.

Likely exposure

Exposure is limited to listed Juniper PTX and QFX10K/QFX10002 platforms with Paradise chipset-based line cards running affected Junos OS releases 17.4 through 20.4 before the fixed versions. Environments relying on BFD for routing convergence face higher operational risk.

Exploitation context

The provided sources do not state active exploitation, and KEV is false. The vulnerability is network-reachable, unauthenticated, low complexity, and availability-only. Impact depends on sustained receipt of high-rate specific packets causing BFD instability.

Researcher notes

The key behavior is failed application of non-default PFE DDoS policer configuration after CLI changes. Validate exposure through asset/version/chipset matching rather than generic Junos presence. Sources do not provide packet details, proof-of-concept status, or workaround specifics beyond fixed releases.

Mitigation direction

  • Upgrade affected Junos OS releases to the fixed versions listed by Juniper or later.
  • Confirm platform and line-card chipset before treating a device as affected.
  • Review Juniper JSA11184 for vendor-specific remediation guidance.
  • Monitor BFD session stability and routing adjacency changes until remediation completes.
  • Do not rely on custom ddos-protection CLI changes as a complete mitigation.

Validation and detection

  • Inventory PTX and QFX10K/QFX10002 devices and installed Junos OS versions.
  • Identify Paradise chipset-based line cards in affected platforms.
  • Compare running releases against Juniper's fixed-version list.
  • Review BFD flap logs and routing protocol instability around high packet-rate events.
  • Verify upgraded devices retain expected routing and BFD stability.
Prepared
Confidence
high
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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cwe · low confidence lookup

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cve · low confidence lookup

CVE-2021-0280 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2021-0280Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Juniper NetworksJunos OS17.4, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2, 20.3, 20.4Listed
Weakness

CWE details

CWE-665

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CWE-665 · source CWE mapping

Improper Initialization

Improper Initialization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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