CVE-2021-0241

Sustained DHCPv6 denial of service via daemon crashes

Published Apr 22, 2021 · Updated Sep 16, 2024

Denial of service in JDHCPD in Juniper Networks Junos OS allows remote attackers to restart the daemon with a crafted DHCPv6 packet. JDHCPD fails to handle a specific DHCPv6 packet and exits with a core dump, after which Junos OS automatically restarts it. The device must operate as a DHCPv6 local server or relay agent, and repeated packets sustain the service interruption; DHCPv4 is unaffected.

CVSS severity7.4
High
EPSS probability0.40%
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 JDHCPD in Juniper Networks Junos OS allows remote attackers to restart the daemon with a crafted DHCPv6 packet. JDHCPD fails to handle a specific DHCPv6 packet and exits with a core dump, after which Junos OS automatically restarts it. The device must operate as a DHCPv6 local server or relay agent, and repeated packets sustain the service interruption; DHCPv4 is unaffected.

The record

CVE
CVE-2021-0241
Published
Apr 22, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-703, T1499.004
Attack vector
adjacent
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=17.3 <17.3R3-S11
  2. Affected versionversion=17.4 <17.4R3-S4
  3. Affected versionversion=18.1 <18.1R3-S12
  4. Affected versionversion=18.2 <18.2R3-S7
  5. Affected versionversion=18.3 <18.3R3-S4
  6. Affected versionversion=18.4 <18.4R3-S7
  7. Affected versionversion=19.1 <19.1R3-S4
  8. Affected versionversion=19.2 <19.2R3-S1
  9. Affected versionversion=19.3 <19.3R3-S1, 19.3R3-S2
  10. Affected versionversion=19.4 <19.4R3-S1
  11. Affected versionversion=20.1 <20.1R2, 20.1R3
  12. Affected versionversion=20.2 <20.2R2, 20.2R3
  13. Affected versionversion=20.3 <20.3R1-S2, 20.3R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

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

Published CVSS scores

7.8NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.4Juniper NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/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-703Improper Check or Handling of Exceptional Conditions
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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