CVE-2021-0294Network attack vector

Partial denial of service via missing storm filter

Published Jul 15, 2021 · Updated Sep 17, 2024

A denial-of-service vulnerability in Juniper Networks Junos OS 18.4R2-S5 allows remote attackers to cause high CPU usage or packet loss via broadcast or unknown-unicast floods. When storm-control enhanced is configured on affected QFX5000 or EX4600 devices, an inconsistently implemented function fails to install the enhanced storm-control filter group, so the traffic is not controlled and service availability can be degraded.

CVSS severity5.0
Medium
EPSS probability0.95%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A denial-of-service vulnerability in Juniper Networks Junos OS 18.4R2-S5 allows remote attackers to cause high CPU usage or packet loss via broadcast or unknown-unicast floods. When storm-control enhanced is configured on affected QFX5000 or EX4600 devices, an inconsistently implemented function fails to install the enhanced storm-control filter group, so the traffic is not controlled and service availability can be degraded.

The record

CVE
CVE-2021-0294
Published
Jul 15, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-474, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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=18.4R2-S5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=18.4R2-S5

Published CVSS scores

5.3Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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-474Use of Function with Inconsistent Implementations
T1499Endpoint 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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