CVE-2021-0226

IPv6 BGP session termination via specific packet

Published Apr 22, 2021 · Updated Sep 17, 2024

Denial of service in Juniper Networks Junos OS Evolved 19.4, 20.1, 20.2, and 20.3 allows remote attackers to terminate IPv6 BGP sessions. A specific IPv6 packet sent to an established internal or external BGP peer session causes that session to terminate; Juniper has not disclosed the affected parser or initialization operation. The peer must use IPv6, and continued packet delivery keeps the BGP session unavailable; IPv4 BGP sessions and Junos OS are unaffected.

CVSS severity7.1
High
EPSS probability0.88%
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 Juniper Networks Junos OS Evolved 19.4, 20.1, 20.2, and 20.3 allows remote attackers to terminate IPv6 BGP sessions. A specific IPv6 packet sent to an established internal or external BGP peer session causes that session to terminate; Juniper has not disclosed the affected parser or initialization operation. The peer must use IPv6, and continued packet delivery keeps the BGP session unavailable; IPv4 BGP sessions and Junos OS are unaffected.

The record

CVE
CVE-2021-0226
Published
Apr 22, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS Evolved
Classifications
CWE-665, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 22, 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=19.4-EVO <19.4R2-S3-EVO
  2. Affected versionversion=20.1-EVO <20.1R2-S3-EVO
  3. Affected versionversion=20.2-EVO <20.2R2-S1-EVO
  4. Affected versionversion=20.3-EVO <20.3R2-EVO

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OS Evolvedversion=19.4-EVO <19.4R2-S3-EVO; version=20.1-EVO <20.1R2-S3-EVO; version=20.2-EVO <20.2R2-S1-EVO; version=20.3-EVO <20.3R2-EVO

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.1Juniper NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
7.5NIST NVDCVSS:3.1/AV:N/AC:L/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.

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-665Improper Initialization
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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