CVE-2021-31378Network attack vector

Subscriber service interruption via spoofed RADIUS responses

Published Oct 19, 2021 · Updated Sep 16, 2024

Denial of service in Juniper Networks Junos OS allows remote attackers to interrupt subscriber network access via spoofed RADIUS messages. During subscriber logout, authd accepts spoofed messages appearing to come from a trusted RADIUS server and leaves the subscriber in a nonrecovering Terminating state. The device must use RADIUS for broadband subscriber access, and the affected subscriber loses network access while spoofing continues.

CVSS severity6.8
Medium
EPSS probability1.01%
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 allows remote attackers to interrupt subscriber network access via spoofed RADIUS messages. During subscriber logout, authd accepts spoofed messages appearing to come from a trusted RADIUS server and leaves the subscriber in a nonrecovering Terminating state. The device must use RADIUS for broadband subscriber access, and the affected subscriber loses network access while spoofing continues.

The record

CVE
CVE-2021-31378
Published
Oct 19, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-772, T1498
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 19, 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-S12
  2. Affected versionversion=17.4 <17.4R3-S5
  3. Affected versionversion=18.1 <18.1R3-S13
  4. Affected versionversion=18.2 <18.2R3-S8
  5. Affected versionversion=18.3 <18.3R3-S5
  6. Affected versionversion=18.4 <18.4R2-S8, 18.4R3-S9
  7. Affected versionversion=19.1 <19.1R3-S6
  8. Affected versionversion=19.2 <19.2R1-S7, 19.2R3-S3
  9. Affected versionversion=19.3 <19.3R2-S6, 19.3R3-S3
  10. Affected versionversion=19.4 <19.4R1-S4, 19.4R1-S4, 19.4R3-S3
  11. Affected versionversion=20.1 <20.1R3
  12. Affected versionversion=20.2 <20.2R3-S1
  13. Affected versionversion=20.3 <20.3R3
  14. Affected versionversion=20.4 <20.4R3
  15. Affected versionversion=21.1 <21.1R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=17.3 <17.3R3-S12; version=17.4 <17.4R3-S5; version=18.1 <18.1R3-S13; version=18.2 <18.2R3-S8; version=18.3 <18.3R3-S5; version=18.4 <18.4R2-S8, 18.4R3-S9; version=19.1 <19.1R3-S6; version=19.2 <19.2R1-S7, 19.2R3-S3; version=19.3 <19.3R2-S6, 19.3R3-S3; version=19.4 <19.4R1-S4, 19.4R1-S4, 19.4R3-S3; version=20.1 <20.1R3; version=20.2 <20.2R3-S1; version=20.3 <20.3R3; version=20.4 <20.4R3; version=21.1 <21.1R2

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
6.8Juniper Networks, Inc.CVSS:3.1/AV:N/AC:H/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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-772Missing Release of Resource after Effective Lifetime
T1498Network 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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