CVE-2021-0217

Adjacent-client service interruption via unbounded DHCP packet processing

Published Jan 15, 2021 · Updated Sep 17, 2024

Resource exhaustion in Juniper Networks Junos OS on EX and QFX Series switches allows adjacent attackers to interrupt traffic forwarding. Processing certain DHCP packets consumes Packet DMA memory without an effective bound, allowing repeated traffic to drive the heap to 99% utilization. The switch must have a DHCP local or relay server configured; exhaustion stops forwarding or crashes fxpc and destabilizes the system.

CVSS severity7.4
High
EPSS probability0.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Juniper Networks Junos OS on EX and QFX Series switches allows adjacent attackers to interrupt traffic forwarding. Processing certain DHCP packets consumes Packet DMA memory without an effective bound, allowing repeated traffic to drive the heap to 99% utilization. The switch must have a DHCP local or relay server configured; exhaustion stops forwarding or crashes fxpc and destabilizes the system.

The record

CVE
CVE-2021-0217
Published
Jan 15, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-119, CWE-770, T1499.001
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 15, 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

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=17.4 <17.4R3-S3
  2. Affected versionversion=18.1R3-S6 <18.1* changes=[{"at":"18.1R3-S11","status":"unaffected"}]
  3. Affected versionversion=18.2R3 <18.2* changes=[{"at":"18.2R3-S6","status":"unaffected"}]
  4. Affected versionversion=18.3R3 <18.3* changes=[{"at":"18.3R3-S4","status":"unaffected"}]
  5. Affected versionversion=18.4R2 <18.4* changes=[{"at":"18.4R3","status":"affected"},{"at":"18.4R2-S5, 18.4R3-S6","status":"unaffected"}]
  6. Affected versionversion=19.1R2 <19.1* changes=[{"at":"19.1R3-S3","status":"unaffected"}]
  7. Affected versionversion=19.2 <19.2R3-S1
  8. Affected versionversion=19.3 <19.3R2-S5, 19.3R3
  9. Affected versionversion=19.4 <19.4R2-S2, 19.4R3
  10. Affected versionversion=20.1 <20.1R2
  11. Affected versionversion=20.2 <20.2R1-S2, 20.2R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=17.4 <17.4R3-S3; version=18.1R3-S6 <18.1* changes=[{"at":"18.1R3-S11","status":"unaffected"}]; version=18.2R3 <18.2* changes=[{"at":"18.2R3-S6","status":"unaffected"}]; version=18.3R3 <18.3* changes=[{"at":"18.3R3-S4","status":"unaffected"}]; version=18.4R2 <18.4* changes=[{"at":"18.4R3","status":"affected"},{"at":"18.4R2-S5, 18.4R3-S6","status":"unaffected"}]; version=19.1R2 <19.1* changes=[{"at":"19.1R3-S3","status":"unaffected"}]; version=19.2 <19.2R3-S1; version=19.3 <19.3R2-S5, 19.3R3; version=19.4 <19.4R2-S2, 19.4R3; version=20.1 <20.1R2; version=20.2 <20.2R1-S2, 20.2R2

Published CVSS scores

7.4Juniper Networks, Inc.CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
3.3NIST NVDAV:A/AC:L/Au:N/C:N/I:N/A:P

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-770Allocation of Resources Without Limits or Throttling
T1499.001OS Exhaustion Flood

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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