CVE-2026-21921

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

MEDIUM

6.5

CVSS Score

Published: January 15, 2026 at 08:28 PM UTC

Updated: June 17, 2026 at 10:19 AM UTC

3 products affected across 2 vendorsJunosJunos OS EvolvedJunos OS Evolved

Using Junos OS by Juniper Networks?

Get instant alerts when new vulnerabilities affect Junos OS - before attackers find them.

Real-time alertsTrack your software stackFree plan available

Start Free Sign In

Severity

MEDIUM6.5

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Junos · Juniper Networks

95%

v < 22.4v < 22.4R3-S823.2 ≤ v < 23.2R2-S523.4 ≤ v < 23.4R222.4 22.4 r1 22.4 r1-s1 22.4 r1-s2 22.4 r2 22.4 r2-s1 22.4 r2-s2 22.4 r3 22.4 r3-s1 22.4 r3-s2 22.4 r3-s3 22.4 r3-s4 22.4 r3-s5 22.4 r3-s6 22.4 r3-s7 23.2 23.2 r1 23.2 r1-s1 23.2 r1-s2 23.2 r2 23.2 r2-s1 23.2 r2-s2 23.2 r2-s3 23.2 r2-s4 23.4 23.4 r1 23.4 r1-s1 23.4 r1-s2

Affected range stops below 22.4R3-S8, so it looks safe — our inference, not a vendor statement

Affected range stops below 23.2R2-S5, so it looks safe — our inference, not a vendor statement

Affected range stops below 23.4R2, so it looks safe — our inference, not a vendor statement

Junos OS Evolved · Juniper Networks

60%

v < 22.4R3-S8-EVO23.2 ≤ v < 23.2R2-S5-EVO23.4 ≤ v < 23.4R2-EVO23.2 23.4

Affected range stops below 22.4R3-S8-EVO, so it looks safe — our inference, not a vendor statement

Affected range stops below 23.2R2-S5-EVO, so it looks safe — our inference, not a vendor statement

Affected range stops below 23.4R2-EVO, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

Vendor Advisory

Source: cverecord

https://supportportal.juniper.net/JSA106021

Vendor Advisory

Source: cverecord

https://kb.juniper.net/JSA106021

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.5MEDIUMjuniper

Attack Vector: NETWORK
Complexity: LOW
Privileges: LOW
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusANALYZED

CWE

CWE-416

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Create account Sign in

Free plan, no card