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Full vulnerability report · 2021
CVE-2021-31365High confidence

Junos OS: EX2300, EX3400 and EX4300 Series: An Aggregated Ethernet (AE) interface will go down due to a stream of specific layer 2 frames

Juniper Networks · Junos OS

6.5MediumCVSS 3.1
Recommended action
Scheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.40% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Juniper Networks Junos OS and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2021-18275

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionScheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
01

What, why and how

An Uncontrolled Resource Consumption vulnerability in Juniper Networks Junos OS on EX2300, EX3400 and EX4300 Series platforms allows an adjacent attacker sending a stream of layer 2 frames will trigger an Aggregated Ethernet (AE) interface to go down and thereby causing a Denial of Service (DoS). By continuously sending a stream of specific layer 2 frames an attacker will sustain the Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS EX4300 Series All versions prior to 15.1R7-S7; 16.1 versions prior to 16.1R7-S8; 17.1 versions prior to 17.1R2-S12; 17.2 versions prior to 17.2R3-S4; 17.3 versions prior to 17.3R3-S8; 17.4 versions prior to 17.4R2-S10, 17.4R3-S2; 18.1 versions prior to 18.1R3-S10; 18.2 versions prior to 18.2R2-S7, 18.2R3-S3; 18.3 versions prior to 18.3R2-S4, 18.3R3-S2; 18.4 versions prior to 18.4R1-S7, 18.4R2-S4, 18.4R3-S1; 19.1 versions prior to 19.1R1-S5, 19.1R2-S1, 19.1R3; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S2, 19.3R3; 19.4 versions prior to 19.4R1-S2, 19.4R2. Juniper Networks Junos OS EX3400 and EX4300-MP Series All versions prior to 18.1R3-S12; 18.2 versions prior to 18.2R3-S7; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R2-S9, 18.4R3-S7; 19.1 versions prior to 19.1R2-S3, 19.1R3-S4; 19.2 versions prior to 19.2R3-S1; 19.3 versions prior to 19.3R3-S1; 19.4 versions prior to 19.4R3-S1; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R3; 20.3 versions prior to 20.3R2. Juniper Networks Junos OS EX2300 Series All versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S9, 18.4R3-S9; 19.1 versions prior to 19.1R2-S3, 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S7, 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R2-S2, 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3-S1; 20.4 versions prior to 20.4R2-S1, 20.4R3; 21.1 versions prior to 21.1R2.

What

An Uncontrolled Resource Consumption vulnerability in Juniper Networks Junos OS on EX2300, EX3400 and EX4300 Series platforms allows an adjacent attacker sending a stream of layer 2 frames will trigger an Aggregated Ethernet (AE) interface to go down and thereby causing a Denial of Service (DoS). By continuously sending a stream of specific layer 2 frames an attacker will sustain the Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS EX4300 Series All versions prior to 15.1R7-S7; 16.1 versions prior to 16.1R7-S8; 17.1 versions prior to 17.1R2-S12; 17.2 versions prior to 17.2R3-S4; 17.3 versions prior to 17.3R3-S8; 17.4 versions prior to 17.4R2-S10, 17.4R3-S2; 18.1 versions prior to 18.1R3-S10; 18.2 versions prior to 18.2R2-S7, 18.2R3-S3; 18.3 versions prior to 18.3R2-S4, 18.3R3-S2; 18.4 versions prior to 18.4R1-S7, 18.4R2-S4, 18.4R3-S1; 19.1 versions prior to 19.1R1-S5, 19.1R2-S1, 19.1R3; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S2, 19.3R3; 19.4 versions prior to 19.4R1-S2, 19.4R2. Juniper Networks Junos OS EX3400 and EX4300-MP Series All versions prior to 18.1R3-S12; 18.2 versions prior to 18.2R3-S7; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R2-S9, 18.4R3-S7; 19.1 versions prior to 19.1R2-S3, 19.1R3-S4; 19.2 versions prior to 19.2R3-S1; 19.3 versions prior to 19.3R3-S1; 19.4 versions prior to 19.4R3-S1; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R3; 20.3 versions prior to 20.3R2. Juniper Networks Junos OS EX2300 Series All versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S9, 18.4R3-S9; 19.1 versions prior to 19.1R2-S3, 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S7, 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R2-S2, 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3-S1; 20.4 versions prior to 20.4R2-S1, 20.4R3; 21.1 versions prior to 21.1R2.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through an adjacent network may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

An Uncontrolled Resource Consumption vulnerability in Juniper Networks Junos OS on EX2300, EX3400 and EX4300 Series platforms allows an adjacent attacker sending a stream of layer 2 frames will trigger an Aggregated Ethernet (AE) interface to go down and thereby causing a Denial of Service (DoS). By continuously sending a stream of specific layer 2 frames an attacker will sustain the Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS EX4300 Series All versions prior to 15.1R7-S7; 16.1 versions prior to 16.1R7-S8; 17.1 versions prior to 17.1R2-S12; 17.2 versions prior to 17.2R3-S4; 17.3 versions prior to 17.3R3-S8; 17.4 versions prior to 17.4R2-S10, 17.4R3-S2; 18.1 versions prior to 18.1R3-S10; 18.2 versions prior to 18.2R2-S7, 18.2R3-S3; 18.3 versions prior to 18.3R2-S4, 18.3R3-S2; 18.4 versions prior to 18.4R1-S7, 18.4R2-S4, 18.4R3-S1; 19.1 versions prior to 19.1R1-S5, 19.1R2-S1, 19.1R3; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S2, 19.3R3; 19.4 versions prior to 19.4R1-S2, 19.4R2. Juniper Networks Junos OS EX3400 and EX4300-MP Series All versions prior to 18.1R3-S12; 18.2 versions prior to 18.2R3-S7; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R2-S9, 18.4R3-S7; 19.1 versions prior to 19.1R2-S3, 19.1R3-S4; 19.2 versions prior to 19.2R3-S1; 19.3 versions prior to 19.3R3-S1; 19.4 versions prior to 19.4R3-S1; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R3; 20.3 versions prior to 20.3R2. Juniper Networks Junos OS EX2300 Series All versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S9, 18.4R3-S9; 19.1 versions prior to 19.1R2-S3, 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S7, 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R2-S2, 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3-S1; 20.4 versions prior to 20.4R2-S1, 20.4R3; 21.1 versions prior to 21.1R2.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through an adjacent network may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
an adjacent network → Uncontrolled Resource Consumption → disrupt the affected service
Attack surface
Adjacent
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-400 ↗

CWE-400: Uncontrolled Resource Consumption. The product does not properly control the allocation and maintenance of a limited resource.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVAdjacentAttack vector: The attacker must be on an adjacent or logically close network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
UnauthenticatedDenial of serviceCWE-400
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

Cyber Security Agency of Singapore · English · CSA-SB-20211020Security Bulletin 20 Oct 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 20 Oct 2021, published on 20 October 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-013301EX シリーズ プラットフォーム上の Juniper Networks Junos OS におけるリソースの枯渇に関する脆弱性

EX2300、EX3400、EX4300 シリーズ プラットフォーム上の Juniper Networks Junos OS には、リソースの枯渇に関する脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Junos OS: unspecified < 15.1R7-S7, 16.1 < 16.1R7-S8, 17.1 < 17.1R2-S12, 17.2 < 17.2R3-S4, 17.3 < 17.3R3-S8, 17.4 < 17.4R2-S10, 17.4R3-S2, 18.1 < 18.1R3-S10, 18.2 < 18.2R2-S7, 18.2R3-S3, 18.3 < 18.3R2-S4, 18.3R3-S2, 18.4 < 18.4R1-S7, 18.4R2-S4, 18.4R3-S1, 19.1 < 19.1R1-S5, 19.1R2-S1, 19.1R3, 19.2 < 19.2R1-S5, 19.2R2, 19.3 < 19.3R2-S2, 19.3R3, 19.4 < 19.4R1-S2, 19.4R2, unspecified < 18.1R3-S12, 18.2 < 18.2R3-S7, 18.3 < 18.3R3-S4, 18.4 < 18.4R2-S9, 18.4R3-S7, 19.1 < 19.1R2-S3, 19.1R3-S4, 19.2 < 19.2R3-S1, 19.3 < 19.3R3-S1, 19.4 < 19.4R3-S1, 20.1 < 20.1R3, 20.2 < 20.2R3, 20.3 < 20.3R2, unspecified < 18.3R3-S5, 18.4 < 18.4R2-S9, 18.4R3-S9, 19.1 < 19.1R2-S3, 19.1R3-S6, 19.2 < 19.2R1-S7, 19.2R3-S3, 19.3 < 19.3R2-S7, 19.3R3-S3, 19.4 < 19.4R3-S5, 20.1 < 20.1R2-S2, 20.1R3-S1, 20.2 < 20.2R3-S2, 20.3 < 20.3R3-S1, 20.4 < 20.4R2-S1, 20.4R3, 21.1 < 21.1R2
Fixed
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 19 Oct 2021 · Last source change 16 Sept 2024, 20:52 UTC · CWE-400 · Uncontrolled Resource Consumption

CVE recordCVE.org · 5.1
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2021-18275
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
ENISA EUVD · EUVD-2021-18275↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2021-31365 · cve.blacktree.nl