CVE-2026-21921

published 2026-01-15

CVE-2026-21921: 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…

Priority P3 39 medium 6.5 CVSS 3.1

AV N AC L PR L UI N S U C N I N A H

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.

Affected

15 ranges

Vendor	Product	Version range	Fixed in
juniper	junos	< 22.4	22.4
juniper	junos	—	—
juniper	junos	—	—
juniper	junos	—	—
juniper	junos_os	—	—
juniper	junos_os_evolved	< 22.4	22.4
juniper	junos_os_evolved	—	—
juniper	junos_os_evolved	—	—
juniper	junos_os_evolved	—	—
juniper_networks	junos_os	< 22.4R3-S8	22.4R3-S8
juniper_networks	junos_os	>= 23.2 < 23.2R2-S5	23.2R2-S5
juniper_networks	junos_os	>= 23.4 < 23.4R2	23.4R2
juniper_networks	junos_os_evolved	< 22.4R3-S8-EVO	22.4R3-S8-EVO
juniper_networks	junos_os_evolved	>= 23.2 < 23.2R2-S5-EVO	23.2R2-S5-EVO
juniper_networks	junos_os_evolved	>= 23.4 < 23.4R2-EVO	23.4R2-EVO

CVSS provenance

nvd v3.1 6.5 MEDIUM CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd v4.0 7.1 HIGH CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:X/RE:M/U:X

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