CVE-2026-21921
Junos OS and Junos OS Evolved: When telemetry collectors are frequently subscribing and unsubscribing to sensors chassisd or rpd will crash
- State
- Published
- Severity
- 7.1 High
- Published
- Jan 15, 2026
- Updated
- Jan 15, 2026
- Reserved
- Jan 5, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 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/AU:Y/R:A/RE:M | juniper |
| 3.1 | 6.5 Medium | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | juniper |
Weaknesses
- CWE-416 Use After Free
Affected Products
| Product | Versions |
|---|---|
Junos OSJuniper Networks |
|
Junos OS EvolvedJuniper Networks |
|
References
- https://supportportal.juniper.net/JSA106021vendor-advisory
- https://kb.juniper.net/JSA106021vendor-advisory
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