CVE-2021-0284Network attack vector

Device shutdown via unchecked TCP/IP packet copy

Published Aug 17, 2021 · Updated Sep 16, 2024

Buffer overflow in the TCP/IP stack of Juniper Networks Junos OS allows remote attackers to shut down affected network devices. The stack copies data from specific packet sequences without checking that it fits the destination buffer, causing the kernel to crash and restart. Only packets addressed to the device trigger the flaw; transit traffic does not, and repeated sequences sustain the shutdown condition.

CVSS severity7.5
High
EPSS probability0.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in the TCP/IP stack of Juniper Networks Junos OS allows remote attackers to shut down affected network devices. The stack copies data from specific packet sequences without checking that it fits the destination buffer, causing the kernel to crash and restart. Only packets addressed to the device trigger the flaw; transit traffic does not, and repeated sequences sustain the shutdown condition.

The record

CVE
CVE-2021-0284
Published
Aug 17, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-120, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 17, 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=12.3 <12.3R12-S19
  2. Affected versionversion=15.1 <15.1R7-S10
  3. Affected versionversion=17.3 <17.3R3-S12
  4. Affected versionversion=18.4 <18.4R2-S9, 18.4R3-S9
  5. Affected versionversion=19.1 <19.1R3-S7
  6. Affected versionversion=19.2 <19.2R1-S7, 19.2R3-S3
  7. Affected versionversion=19.3 <19.3R2-S7, 19.3R3-S3
  8. Affected versionversion=19.4 <19.4R3-S5
  9. Affected versionversion=20.1 <20.1R3-S1
  10. Affected versionversion=20.2 <20.2R3-S2
  11. Affected versionversion=20.3 <20.3R3-S1
  12. Affected versionversion=20.4 <20.4R2-S2, 20.4R3
  13. Affected versionversion=21.1 <21.1R2
  14. Affected versionversion=21.2 <21.2R1-S1, 21.2R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=12.3 <12.3R12-S19; version=15.1 <15.1R7-S10; version=17.3 <17.3R3-S12; version=18.4 <18.4R2-S9, 18.4R3-S9; version=19.1 <19.1R3-S7; version=19.2 <19.2R1-S7, 19.2R3-S3; version=19.3 <19.3R2-S7, 19.3R3-S3; version=19.4 <19.4R3-S5; version=20.1 <20.1R3-S1; version=20.2 <20.2R3-S2; version=20.3 <20.3R3-S1; version=20.4 <20.4R2-S2, 20.4R3; version=21.1 <21.1R2; version=21.2 <21.2R1-S1, 21.2R2

Published CVSS scores

7.5Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.8NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:C

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 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-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
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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