CVE-2026-21921: When telemetry collectors are frequently subscribing and unsubscribing to sensors chassisd or rpd will crash

Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.

Affected and fixed versions

Product / branch	Fixed in
Junos OS 0	22.4R3-S8 or later
Junos OS 23.2	23.2R2-S5 or later
Junos OS 23.4	23.4R2 or later
Junos OS Evolved 0	22.4R3-S8-EVO or later
Junos OS Evolved 23.2	23.2R2-S5-EVO or later
Junos OS Evolved 23.4	23.4R2-EVO or later

Always confirm against the vendor advisory, which lists every fixed hotfix.

What it is

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.

Am I affected?

A device is only exposed to this issue if GRPC services are configured:

[ system services extension-service request-response grpc ]

Workarounds

There are no known workarounds for this issue.

Exploitation

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.