CVE-2021-31365

Adjacent DoS via crafted Layer 2 frame stream

Published Oct 19, 2021 · Updated Sep 16, 2024

Uncontrolled resource consumption in Junos OS on EX2300, EX3400 and EX4300 allows adjacent attackers to cause DoS via Layer 2 frames. With LACP and LLDP enabled on an Aggregated Ethernet interface, a stream of specific frames drives the AE interface down and keeps the service unavailable. The attacker needs adjacent network access but no authentication; disabling LLDP prevents the condition, and Juniper reports no known malicious exploitation.

CVSS severity6.5
Medium
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in Junos OS on EX2300, EX3400 and EX4300 allows adjacent attackers to cause DoS via Layer 2 frames. With LACP and LLDP enabled on an Aggregated Ethernet interface, a stream of specific frames drives the AE interface down and keeps the service unavailable. The attacker needs adjacent network access but no authentication; disabling LLDP prevents the condition, and Juniper reports no known malicious exploitation.

The record

CVE
CVE-2021-31365
Published
Oct 19, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-400, T1498
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=16.1 <16.1R7-S8
  2. Affected versionversion=17.1 <17.1R2-S12
  3. Affected versionversion=17.2 <17.2R3-S4
  4. Affected versionversion=17.3 <17.3R3-S8
  5. Affected versionversion=17.4 <17.4R2-S10, 17.4R3-S2
  6. Affected versionversion=18.1 <18.1R3-S10
  7. Affected versionversion=18.2 <18.2R2-S7, 18.2R3-S3
  8. Affected versionversion=18.2 <18.2R3-S7
  9. Affected versionversion=18.3 <18.3R2-S4, 18.3R3-S2
  10. Affected versionversion=18.3 <18.3R3-S4
  11. Affected versionversion=18.4 <18.4R1-S7, 18.4R2-S4, 18.4R3-S1
  12. Affected versionversion=18.4 <18.4R2-S9, 18.4R3-S7
  13. Affected versionversion=18.4 <18.4R2-S9, 18.4R3-S9
  14. Affected versionversion=19.1 <19.1R1-S5, 19.1R2-S1, 19.1R3
  15. Affected versionversion=19.1 <19.1R2-S3, 19.1R3-S4
  16. Affected versionversion=19.1 <19.1R2-S3, 19.1R3-S6
  17. Affected versionversion=19.2 <19.2R1-S5, 19.2R2
  18. Affected versionversion=19.2 <19.2R1-S7, 19.2R3-S3
  19. Affected versionversion=19.2 <19.2R3-S1
  20. Affected versionversion=19.3 <19.3R2-S2, 19.3R3
  21. Affected versionversion=19.3 <19.3R2-S7, 19.3R3-S3
  22. Affected versionversion=19.3 <19.3R3-S1
  23. Affected versionversion=19.4 <19.4R1-S2, 19.4R2
  24. Affected versionversion=19.4 <19.4R3-S1
  25. Affected versionversion=19.4 <19.4R3-S5
  26. Affected versionversion=20.1 <20.1R2-S2, 20.1R3-S1
  27. Affected versionversion=20.1 <20.1R3
  28. Affected versionversion=20.2 <20.2R3
  29. Affected versionversion=20.2 <20.2R3-S2
  30. Affected versionversion=20.3 <20.3R2
  31. Affected versionversion=20.3 <20.3R3-S1
  32. Affected versionversion=20.4 <20.4R2-S1, 20.4R3
  33. Affected versionversion=21.1 <21.1R2
  34. Affected versionversion=unspecified <15.1R7-S7
  35. Affected versionversion=unspecified <18.1R3-S12
  36. Affected versionversion=unspecified <18.3R3-S5

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=16.1 <16.1R7-S8; version=17.1 <17.1R2-S12; version=17.2 <17.2R3-S4; version=17.3 <17.3R3-S8; version=17.4 <17.4R2-S10, 17.4R3-S2; version=18.1 <18.1R3-S10; version=18.2 <18.2R2-S7, 18.2R3-S3; version=18.2 <18.2R3-S7; version=18.3 <18.3R2-S4, 18.3R3-S2; version=18.3 <18.3R3-S4; version=18.4 <18.4R1-S7, 18.4R2-S4, 18.4R3-S1; version=18.4 <18.4R2-S9, 18.4R3-S7; version=18.4 <18.4R2-S9, 18.4R3-S9; version=19.1 <19.1R1-S5, 19.1R2-S1, 19.1R3; version=19.1 <19.1R2-S3, 19.1R3-S4; version=19.1 <19.1R2-S3, 19.1R3-S6; version=19.2 <19.2R1-S5, 19.2R2; version=19.2 <19.2R1-S7, 19.2R3-S3; version=19.2 <19.2R3-S1; version=19.3 <19.3R2-S2, 19.3R3; version=19.3 <19.3R2-S7, 19.3R3-S3; version=19.3 <19.3R3-S1; version=19.4 <19.4R1-S2, 19.4R2; version=19.4 <19.4R3-S1; version=19.4 <19.4R3-S5; version=20.1 <20.1R2-S2, 20.1R3-S1; version=20.1 <20.1R3; version=20.2 <20.2R3; version=20.2 <20.2R3-S2; version=20.3 <20.3R2; version=20.3 <20.3R3-S1; version=20.4 <20.4R2-S1, 20.4R3; version=21.1 <21.1R2; version=unspecified <15.1R7-S7; version=unspecified <18.1R3-S12; version=unspecified <18.3R3-S5

Published CVSS scores

6.5Juniper NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1498Network Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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