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CVE-2026-21921

Junos OS and Junos OS Evolved: When telemetry collectors are frequently subscribing and unsubscribing to sensors chassisd or rpd will crash

Published: Jan 15, 2026Updated: Jan 23, 2026 Sources: CVE List NVDCWE-416
NVD MITRE
6.5CVSSMEDIUM
EPSS Score
0.3%
Top 74.9%
CISA KEV
Not in KEV
Exploits
0 Known
Remediation
Patch Available

Description

A Use After Free vulnerability in the chassis daemon (chassisd) of Juniper Networks Junos OS and Junos OS Evolved allows a network-based attacker authenticated with low privileges to cause a Denial-of-Service (DoS). When telemetry collectors are frequently subscribing and unsubscribing to sensors continuously over a long period of time, telemetry-capable processes like chassisd, rpd or mib2d will crash and restart, which - depending on the process - can cause a complete outage until the system has recovered. This issue affects:  Junos OS:  * all versions before 22.4R3-S8, * 23.2 versions before 23.2R2-S5, * 23.4 versions before 23.4R2; Junos OS Evolved: * all versions before 22.4R3-S8-EVO, * 23.2 versions before 23.2R2-S5-EVO, * 23.4 versions before 23.4R2-EVO.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-416

Affected Products

junosjuniperNetworking Infrastructure
junos os evolvedjuniperNetworking Infrastructure
Junos OSJuniper NetworksNetworking Infrastructure
Junos OS EvolvedJuniper NetworksNetworking Infrastructure
junipercommercialUSNetworking Infrastructureaka juniper networks, juniper networks inc.
juniper networkscommercialUSNetworking Infrastructure

Attack Graph

Products CVE Techniques Tactics

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Exploitability

0 exploit sources identified

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Official Patch Available
Workaround Available

MITRE ATT&CK

2 techniques
Initial Access
Privilege Escalation
View detailed technique mapping

References

https://kb.juniper.net/JSA106021
kb.juniper.net
https://supportportal.juniper.net/JSA106021
supportportal.juniper.net

Timeline

Published
Jan 15, 2026
Last Updated
Jan 23, 2026

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