CVE-2021-0203Network attack vector

LAN service interruption via ineffective RTG storm control

Published Jan 15, 2021 · Updated Sep 17, 2024

Improper traffic filtering in Junos OS on affected EX and QFX5K releases allows remote attackers to degrade LAN availability. A Storm Control profile applied to an RTG interface fails to drop broadcast, multicast, and unknown-unicast packets after traffic reaches its configured threshold. Exploitation requires an affected EX or QFX5K switch with an RTG and a Storm Control profile, and the resulting excess traffic can interrupt LAN service.

CVSS severity8.6
High
EPSS probability1.00%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper traffic filtering in Junos OS on affected EX and QFX5K releases allows remote attackers to degrade LAN availability. A Storm Control profile applied to an RTG interface fails to drop broadcast, multicast, and unknown-unicast packets after traffic reaches its configured threshold. Exploitation requires an affected EX or QFX5K switch with an RTG and a Storm Control profile, and the resulting excess traffic can interrupt LAN service.

The record

CVE
CVE-2021-0203
Published
Jan 15, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-794, T1498.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 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

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=15.1 <15.1R7-S7
  2. Affected versionversion=16.1 <16.1R7-S8
  3. Affected versionversion=17.2 <17.2R3-S4
  4. Affected versionversion=17.3 <17.3R3-S8
  5. Affected versionversion=17.4 <17.4R2-S11, 17.4R3-S2
  6. Affected versionversion=18.1 <18.1R3-S10
  7. Affected versionversion=18.2 <18.2R3-S5
  8. Affected versionversion=18.3 <18.3R2-S4, 18.3R3-S2
  9. Affected versionversion=18.4 <18.4R2-S5, 18.4R3-S3
  10. Affected versionversion=19.1 <19.1R2-S2, 19.1R3-S2
  11. Affected versionversion=19.2 <19.2R1-S5, 19.2R2-S1, 19.2R3
  12. Affected versionversion=19.3 <19.3R2-S4, 19.3R3
  13. Affected versionversion=19.4 <19.4R1-S3, 19.4R2-S1, 19.4R3
  14. Affected versionversion=20.1 <20.1R1-S2, 20.1R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=15.1 <15.1R7-S7; version=16.1 <16.1R7-S8; version=17.2 <17.2R3-S4; version=17.3 <17.3R3-S8; version=17.4 <17.4R2-S11, 17.4R3-S2; version=18.1 <18.1R3-S10; version=18.2 <18.2R3-S5; version=18.3 <18.3R2-S4, 18.3R3-S2; version=18.4 <18.4R2-S5, 18.4R3-S3; version=19.1 <19.1R2-S2, 19.1R3-S2; version=19.2 <19.2R1-S5, 19.2R2-S1, 19.2R3; version=19.3 <19.3R2-S4, 19.3R3; version=19.4 <19.4R1-S3, 19.4R2-S1, 19.4R3; version=20.1 <20.1R1-S2, 20.1R2

Published CVSS scores

8.6Juniper Networks, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
4.3NIST NVDAV:N/AC:M/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-794Incomplete Filtering of Multiple Instances of Special Elements
T1498.001Direct Network Flood

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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