CVE-2021-0229Network attack vector

Sustained service interruption via MQTT packet stream

Published Apr 22, 2021 · Updated Sep 16, 2024

Uncontrolled resource consumption in the Junos OS MQTT server allows remote attackers to crash and restart the service with specific packets. The server repeatedly receives and processes the packet stream until resource consumption forces recurring crashes and restarts. Exposure requires a JET application with a listening port and the system services extension-service notification configuration; the outage persists while the stream continues.

CVSS severity5.3
Medium
EPSS probability1.16%
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 MQTT server allows remote attackers to crash and restart the service with specific packets. The server repeatedly receives and processes the packet stream until resource consumption forces recurring crashes and restarts. Exposure requires a JET application with a listening port and the system services extension-service notification configuration; the outage persists while the stream continues.

The record

CVE
CVE-2021-0229
Published
Apr 22, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 22, 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=16.1R1 <16.1*
  2. Affected versionversion=17.3 <17.3R3-S11
  3. Affected versionversion=17.4 <17.4R2-S13, 17.4R3-S4
  4. Affected versionversion=18.1 <18.1R3-S12
  5. Affected versionversion=18.2 <18.2R2-S8, 18.2R3-S7
  6. Affected versionversion=18.3 <18.3R3-S4
  7. Affected versionversion=18.4 <18.4R1-S8, 18.4R2-S7, 18.4R3-S7
  8. Affected versionversion=19.1 <19.1R3-S5
  9. Affected versionversion=19.2 <19.2R1-S6, 19.2R3-S2
  10. Affected versionversion=19.3 <19.3R3-S2
  11. Affected versionversion=19.4 <19.4R2-S4, 19.4R3-S2
  12. Affected versionversion=20.1 <20.1R2-S1, 20.1R3
  13. Affected versionversion=20.2 <20.2R2-S2, 20.2R3
  14. Affected versionversion=20.3 <20.3R1-S1, 20.3R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=16.1R1 <16.1*; version=17.3 <17.3R3-S11; version=17.4 <17.4R2-S13, 17.4R3-S4; version=18.1 <18.1R3-S12; version=18.2 <18.2R2-S8, 18.2R3-S7; version=18.3 <18.3R3-S4; version=18.4 <18.4R1-S8, 18.4R2-S7, 18.4R3-S7; version=19.1 <19.1R3-S5; version=19.2 <19.2R1-S6, 19.2R3-S2; version=19.3 <19.3R3-S2; version=19.4 <19.4R2-S4, 19.4R3-S2; version=20.1 <20.1R2-S1, 20.1R3; version=20.2 <20.2R2-S2, 20.2R3; version=20.3 <20.3R1-S1, 20.3R2

Published CVSS scores

5.3Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.0NIST NVDAV: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-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

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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