CVE-2021-0216

Network service interruption via transit ARP flood

Published Apr 22, 2021 · Updated Sep 16, 2024

Denial of service in affected Juniper Networks Junos OS releases allows attackers to disrupt routing with high-rate transit ARP traffic. The affected ACX forwarding path exceptions transit ARP packets to the CPU, where sustained load expires BFD detection timers and flaps sessions. Reachability requires transit traffic on ACX5448 or ACX710 hardware; BFD loss can drop routing adjacencies and interrupt network 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 affected Juniper Networks Junos OS releases allows attackers to disrupt routing with high-rate transit ARP traffic. The affected ACX forwarding path exceptions transit ARP packets to the CPU, where sustained load expires BFD detection timers and flaps sessions. Reachability requires transit traffic on ACX5448 or ACX710 hardware; BFD loss can drop routing adjacencies and interrupt network service.

The record

CVE
CVE-2021-0216
Published
Apr 22, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
T1498.001
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=18.2 <18.2R3-S8
  2. Affected versionversion=18.3 <18.3R3-S5
  3. Affected versionversion=18.4 <18.4R1-S6, 18.4R3-S7
  4. Affected versionversion=19.1 <19.1R3-S5
  5. Affected versionversion=19.2 <19.2R2, 19.2R3
  6. Affected versionversion=19.3 <19.3R3
  7. Affected versionversion=19.4 <19.4R3
  8. Affected versionversion=20.1 <20.1R2
  9. Affected versionversion=20.2 <20.2R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=18.2 <18.2R3-S8; version=18.3 <18.3R3-S5; version=18.4 <18.4R1-S6, 18.4R3-S7; version=19.1 <19.1R3-S5; version=19.2 <19.2R2, 19.2R3; version=19.3 <19.3R3; version=19.4 <19.4R3; version=20.1 <20.1R2; version=20.2 <20.2R2

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.3NIST NVDAV:A/AC:L/Au:N/C:N/I:N/A:P
6.5Juniper NetworksCVSS:3.1/AV:A/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

T1498.001Direct Network Flood

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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