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CVE Record

CVE-2021-0285: Junos OS: QFX5000 Series and EX4600 Series: Continuous traffic destined to a device configured with MC-LAG leading to nodes losing their control connection which can impact traffic

An uncontrolled resource consumption vulnerability in Juniper Networks Junos OS on QFX5000 Series and EX4600 Series switches allows an attacker sending large amounts of legitimate traffic destined to the device to cause Interchassis Control Protocol (ICCP) interruptions, leading to an unstable control connection between the Multi-Chassis Link Aggregation Group (MC-LAG) nodes which can in turn lead to traffic loss. Continued receipt of this amount of traffic will create a sustained Denial of Service (DoS) condition. An indication that the system could be impacted by this issue is the following log message: "DDOS_PROTOCOL_VIOLATION_SET: Warning: Host-bound traffic for protocol/exception LOCALNH:aggregate exceeded its allowed bandwidth at fpc <fpc number> for <n> times, started at <timestamp>" This issue affects Juniper Networks Junos OS on QFX5000 Series and EX4600 Series: 15.1 versions prior to 15.1R7-S9; 17.3 versions prior to 17.3R3-S11; 17.4 versions prior to 17.4R2-S13, 17.4R3-S5; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S8, 18.4R3-S7; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R1-S6, 19.2R3-S2; 19.3 versions prior to 19.3R2-S6, 19.3R3-S2; 19.4 versions prior to 19.4R1-S4, 19.4R2-S4, 19.4R3-S2; 20.1 versions prior to 20.1R2-S2, 20.1R3; 20.2 versions prior to 20.2R2-S3, 20.2R3; 20.3 versions prior to 20.3R2; 20.4 versions prior to 20.4R1-S1, 20.4R2.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Juniper switch running affected Junos OS can lose the control connection between paired MC-LAG nodes when flooded with high volumes of legitimate traffic aimed at the device. That instability can cause traffic loss and a sustained denial of service.

Executive priority

Prioritize remediation on production MC-LAG pairs carrying critical network traffic. The primary business risk is availability disruption, not data theft, but a sustained DoS on core switching can create broad outage impact.

Technical view

CVE-2021-0285 is CWE-770 uncontrolled resource consumption in Junos OS on QFX5000 and EX4600 switches using MC-LAG. Excess host-bound LOCALNH aggregate traffic can interrupt ICCP, destabilizing the MC-LAG control connection and affecting availability.

Likely exposure

Exposure is limited to Juniper QFX5000 Series and EX4600 Series switches running listed vulnerable Junos OS releases, especially devices configured with MC-LAG and reachable by large volumes of traffic destined to the device itself.

Exploitation context

The CVSS vector is network, low complexity, no privileges, no user interaction, with high availability impact. The provided sources do not show CISA KEV listing, public exploit code, or confirmed active exploitation.

Researcher notes

Evidence ties impact to host-bound traffic exceeding allowed bandwidth for LOCALNH aggregate and ICCP interruptions. Sources provide affected and fixed release boundaries, but no exploit details or confirmed in-the-wild activity.

Mitigation direction

  • Identify QFX5000 and EX4600 switches running the affected Junos OS release trains.
  • Upgrade to the fixed Junos OS release for your train per Juniper JSA11187.
  • Review Juniper guidance before applying operational workarounds or configuration changes.
  • Limit unnecessary traffic destined to switch control-plane interfaces where operationally feasible.

Validation and detection

  • Confirm whether each QFX5000 or EX4600 device uses MC-LAG.
  • Compare installed Junos OS versions against the affected version list.
  • Search logs for DDOS_PROTOCOL_VIOLATION_SET involving LOCALNH aggregate traffic.
  • Review ICCP and MC-LAG stability indicators for interruptions or traffic loss.
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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-770: Exact CWE lookup

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Open ATT&CK lookup
cve · low confidence lookup

CVE-2021-0285 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-2021-0285Attack 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 OS15.1, 17.3, 17.4, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2, 20.3, 20.4Listed
Weakness

CWE details

CWE-770

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-770 · source CWE mapping

Allocation of Resources Without Limits or Throttling

Allocation of Resources Without Limits or Throttling represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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