CVE-2021-0242

Device restart via DMA buffer exhaustion

Published Apr 22, 2021 · Updated Sep 17, 2024

Denial of service in Juniper Networks Junos OS on EX4300 switches allows attackers to restart the device with crafted unicast frames. The packet-forwarding path fails to release DMA buffers while processing specific valid unicast frames, so repeated traffic exhausts the FPC buffer pool. Exposure requires an interface without L2PT or dot1x configured; exhaustion crashes the FPC and restarts the switch, interrupting service.

CVSS severity6.5
Medium
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 Juniper Networks Junos OS on EX4300 switches allows attackers to restart the device with crafted unicast frames. The packet-forwarding path fails to release DMA buffers while processing specific valid unicast frames, so repeated traffic exhausts the FPC buffer pool. Exposure requires an interface without L2PT or dot1x configured; exhaustion crashes the FPC and restarts the switch, interrupting service.

The record

CVE
CVE-2021-0242
Published
Apr 22, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-119, CWE-770, CWE-241, T1499
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

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 <17.4R2-S13, 17.4R3-S4
  3. Affected versionversion=18.1 <18.1R3-S12
  4. Affected versionversion=18.2 <18.2R2-S8, 18.2R3-S7
  5. Affected versionversion=18.3 <18.3R3-S4
  6. Affected versionversion=18.4 <18.4R1-S8, 18.4R2-S7, 18.4R3-S7
  7. Affected versionversion=19.1 <19.1R1-S6, 19.1R2-S2, 19.1R3-S4
  8. Affected versionversion=19.2 <19.2R1-S6, 19.2R3-S2
  9. Affected versionversion=19.3 <19.3R3-S2
  10. Affected versionversion=19.4 <19.4R2-S3, 19.4R3-S1
  11. Affected versionversion=20.1 <20.1R2
  12. Affected versionversion=20.2 <20.2R2-S1, 20.2R3
  13. Affected versionversion=20.3 <20.3R1-S1, 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 <17.4R2-S13, 17.4R3-S4; version=18.1 <18.1R3-S12; version=18.2 <18.2R2-S8, 18.2R3-S7; version=18.3 <18.3R3-S4; version=18.4 <18.4R1-S8, 18.4R2-S7, 18.4R3-S7; version=19.1 <19.1R1-S6, 19.1R2-S2, 19.1R3-S4; version=19.2 <19.2R1-S6, 19.2R3-S2; version=19.3 <19.3R3-S2; version=19.4 <19.4R2-S3, 19.4R3-S1; version=20.1 <20.1R2; version=20.2 <20.2R2-S1, 20.2R3; version=20.3 <20.3R1-S1, 20.3R2

Published CVSS scores

6.5Juniper Networks, Inc.CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
6.1NIST NVDAV:A/AC:L/Au:N/C:N/I:N/A:C

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
CWE-241Improper Handling of Unexpected Data Type
T1499Endpoint Denial of Service

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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