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No exploitation reportedFix available

CVE-2021-31378

No exploitation reported by the sources we read.

  • Published2021-10-19
  • WeaknessCWE-772

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

In broadband environments, including but not limited to Enhanced Subscriber Management, (CHAP, PPP, DHCP, etc.), on Juniper Networks Junos OS devices where RADIUS servers are configured for managing subscriber access and a subscriber is logged in and then requests to logout, the subscriber may be forced into a "Terminating" state by an attacker who is able to send spoofed messages appearing to originate from trusted RADIUS server(s) destined to the device in response to the subscriber's request. These spoofed messages cause the Junos OS General Authentication Service (authd) daemon to force the broadband subscriber into this "Terminating" state which the subscriber will not recover from thereby causing a Denial of Service (DoS) to the endpoint device. Once in the "Terminating" state, the endpoint subscriber will no longer be able to access the network. Restarting the authd daemon on the Junos OS device will temporarily clear the subscribers out of the "Terminating" state. As long as the attacker continues to send these spoofed packets and subscribers request to be logged out, the subscribers will be returned to the "Terminating" state thereby creating a persistent Denial of Service to the subscriber. An indicator of compromise may be seen by displaying the output of "show subscribers summary". The presence of subscribers in the "Terminating" state may indicate the issue is occurring. This issue affects: Juniper Networks Junos OS 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S8, 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S3; 19.4 versions prior to 19.4R1-S4, 19.4R1-S4, 19.4R3-S3; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R3-S1; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2. This issue does not affect: Juniper Networks Junos OS 12.3 version 12.3R1 and later versions; 15.1 version 15.1R1 and later versions.

Timeline

dates in UTC
  1. 2021-10-1919:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-31378?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-31378?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Juniper junos
BranchAffectedFixed in
17.3= 17.3no fix published
17.4= 17.4no fix published
18.1= 18.1no fix published
18.2= 18.2no fix published
18.3= 18.3no fix published
18.4= 18.4no fix published
19.1= 19.1no fix published
19.2= 19.2no fix published
19.3= 19.3no fix published
19.4= 19.4no fix published
20.1= 20.1no fix published
20.2= 20.2no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CNACVSS 3.16.8read 2026-10-23
  • NVDCVSS 3.17.5read 2026-10-23
  • NVDCVSS 2.04.3read 2026-10-23
  • CNAweakness (CWE)CWE-772read 2026-10-23
  • NVDweakness (CWE)CWE-772read 2026-10-23
  • FIRST EPSSEPSS score1.0 %2026-10-22

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2021-10-19
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2021-31378?

In broadband environments, including but not limited to Enhanced Subscriber Management, (CHAP, PPP, DHCP, etc.), on Juniper Networks Junos OS devices where RADIUS servers are configured for managing subscriber access and a subscriber is logged in and then requests to logout, the subscriber may be forced into a "Terminating" state by an attacker who is able to send spoofed messages appearing to originate from trusted RADIUS server(s) destined to the device in response to the subscriber's request. These spoofed messages cause the Junos OS General Authentication Service (authd) daemon to force the broadband subscriber into this "Terminating" state which the subscriber will not recover from thereby causing a Denial of Service (DoS) to the endpoint device. Once in the "Terminating" state, the endpoint subscriber will no longer be able to access the network. Restarting the authd daemon on the Junos OS device will temporarily clear the subscribers out of the "Terminating" state. As long as the attacker continues to send these spoofed packets and subscribers request to be logged out, the subscribers will be returned to the "Terminating" state thereby creating a persistent Denial of Service to the subscriber. An indicator of compromise may be seen by displaying the output of "show subscribers summary". The presence of subscribers in the "Terminating" state may indicate the issue is occurring. This issue affects: Juniper Networks Junos OS 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S8, 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S3; 19.4 versions prior to 19.4R1-S4, 19.4R1-S4, 19.4R3-S3; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R3-S1; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2. This issue does not affect: Juniper Networks Junos OS 12.3 version 12.3R1 and later versions; 15.1 version 15.1R1 and later versions.

Is CVE-2021-31378 actively exploited?

Active exploitation of CVE-2021-31378 has not been confirmed. Its EPSS score was 1.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-31378?

CVE-2021-31378 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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