CVE-2021-0258Network attack vector

Kernel panic via concurrent TCPv6 forwarding race

Published Apr 22, 2021 · Updated Sep 16, 2024

Denial of service in affected Juniper Networks Junos OS 17.2 through 19.4 releases allows remote attackers to trigger a kernel panic. The concurrent network stack forwards transit TCPv6 received on the Ethernet management interface without proper synchronization, causing the kernel to panic. The concurrent network stack is enabled by default; traffic destined for the interface and non-TCPv6 transit traffic do not trigger the condition.

CVSS severity5.9
Medium
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in affected Juniper Networks Junos OS 17.2 through 19.4 releases allows remote attackers to trigger a kernel panic. The concurrent network stack forwards transit TCPv6 received on the Ethernet management interface without proper synchronization, causing the kernel to panic. The concurrent network stack is enabled by default; traffic destined for the interface and non-TCPv6 transit traffic do not trigger the condition.

The record

CVE
CVE-2021-0258
Published
Apr 22, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-362, CAPEC-26, 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

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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=17.3 <17.3R3-S9
  2. Affected versionversion=17.4 <17.4R2-S11, 17.4R3-S2
  3. Affected versionversion=18.1 <18.1R3-S11
  4. Affected versionversion=18.2 <18.2R3-S5
  5. Affected versionversion=18.3 <18.3R2-S4, 18.3R3-S3
  6. Affected versionversion=18.4 <18.4R2-S5, 18.4R3-S4
  7. Affected versionversion=19.1 <19.1R2-S2, 19.1R3
  8. Affected versionversion=19.2 <19.2R1-S5, 19.2R2
  9. Affected versionversion=19.3 <19.3R2-S4, 19.3R3
  10. Affected versionversion=19.4 <19.4R1-S3, 19.4R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=17.3 <17.3R3-S9; version=17.4 <17.4R2-S11, 17.4R3-S2; version=18.1 <18.1R3-S11; version=18.2 <18.2R3-S5; version=18.3 <18.3R2-S4, 18.3R3-S3; version=18.4 <18.4R2-S5, 18.4R3-S4; version=19.1 <19.1R2-S2, 19.1R3; version=19.2 <19.2R1-S5, 19.2R2; version=19.3 <19.3R2-S4, 19.3R3; version=19.4 <19.4R1-S3, 19.4R2

Published CVSS scores

7.1NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:N/I:N/A:C
5.9Juniper Networks, Inc.CVSS:3.1/AV:N/AC:H/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-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CAPEC-26Leveraging Race Conditions
T1499.004Application or System Exploitation

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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