CVE-2021-31368Network attack vector

Device hang via management-port traffic flood

Published Oct 19, 2021 · Updated Sep 16, 2024

Uncontrolled resource consumption in the Junos OS kernel allows remote attackers to hang Juniper Networks devices via management-port floods. Traffic received on the out-of-band management Ethernet port drives the kernel and netisr processes to high CPU utilization without effective load control. Unauthenticated network access to that port sustains the service interruption only while the flood continues; the system recovers after it stops.

CVSS severity7.5
High
EPSS probability1.08%
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 the Junos OS kernel allows remote attackers to hang Juniper Networks devices via management-port floods. Traffic received on the out-of-band management Ethernet port drives the kernel and netisr processes to high CPU utilization without effective load control. Unauthenticated network access to that port sustains the service interruption only while the flood continues; the system recovers after it stops.

The record

CVE
CVE-2021-31368
Published
Oct 19, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-400, T1499.001
Attack vector
network
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

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Is a vulnerable build present?

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

  1. Affected versionversion=18.2 <18.2R3-S8
  2. Affected versionversion=18.3 <18.3R3-S5
  3. Affected versionversion=18.4 <18.4R2-S8, 18.4R3-S9
  4. Affected versionversion=19.1 <19.1R3-S5
  5. Affected versionversion=19.2 <19.2R1-S7, 19.2R3-S3
  6. Affected versionversion=19.3 <19.3R2-S6, 19.3R3-S2
  7. Affected versionversion=19.4 <19.4R1-S4, 19.4R3-S3
  8. Affected versionversion=20.1 <20.1R2-S2, 20.1R3
  9. Affected versionversion=20.2 <20.2R3
  10. Affected versionversion=20.3 <20.3R2-S1, 20.3R3
  11. Affected versionversion=20.4 <20.4R2
  12. Affected versionversion=unspecified <18.1R3-S13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=18.2 <18.2R3-S8; version=18.3 <18.3R3-S5; version=18.4 <18.4R2-S8, 18.4R3-S9; version=19.1 <19.1R3-S5; version=19.2 <19.2R1-S7, 19.2R3-S3; version=19.3 <19.3R2-S6, 19.3R3-S2; version=19.4 <19.4R1-S4, 19.4R3-S3; version=20.1 <20.1R2-S2, 20.1R3; version=20.2 <20.2R3; version=20.3 <20.3R2-S1, 20.3R3; version=20.4 <20.4R2; version=unspecified <18.1R3-S13

Published CVSS scores

7.5Juniper NetworksCVSS:3.1/AV:N/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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.001OS Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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