CVE-2021-0267

Service crash via malformed DHCP packet processing

Published Apr 22, 2021 · Updated Sep 17, 2024

Improper input validation in affected Junos OS 19.4, 20.1, 20.2, and 20.3 releases allows attackers to crash jdhcpd with a crafted DHCP packet. The active-lease query path in the JDHCPD DHCP Relay Agent processes the malformed packet without adequate validation, causing the service to core. Exploitation requires active-leasequery to be configured and network adjacency to the device; repeated packets sustain the service interruption.

CVSS severity7.4
High
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in affected Junos OS 19.4, 20.1, 20.2, and 20.3 releases allows attackers to crash jdhcpd with a crafted DHCP packet. The active-lease query path in the JDHCPD DHCP Relay Agent processes the malformed packet without adequate validation, causing the service to core. Exploitation requires active-leasequery to be configured and network adjacency to the device; repeated packets sustain the service interruption.

The record

CVE
CVE-2021-0267
Published
Apr 22, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-20, 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 <19.4R3-S1
  2. Affected versionversion=20.1 <20.1R2-S1, 20.1R3
  3. Affected versionversion=20.2 <20.2R3
  4. Affected versionversion=20.3 <20.3R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=19.4 <19.4R3-S1; version=20.1 <20.1R2-S1, 20.1R3; version=20.2 <20.2R3; version=20.3 <20.3R2

Published CVSS scores

3.3NIST NVDAV:A/AC:L/Au:N/C:N/I:N/A:P
6.5NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.4Juniper NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
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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