Use After Free Vulnerability in Junos OS and Junos OS Evolved by Juniper Networks
CVE-2026-21921

7.1HIGH

Key Information:

Vendor

Juniper Networks
Status
Junos Os
Junos Os Evolved
Vendor
CVE Published:
15 January 2026

Badges

👾 Exploit Exists

What is CVE-2026-21921?

A Use After Free vulnerability exists in the chassis daemon of Juniper Networks' Junos OS and Junos OS Evolved. This flaw permits an attacker with low privileges to initiate a Denial-of-Service condition. Under certain conditions, particularly when telemetry collectors continually subscribe and unsubscribe to sensors over an extended duration, critical telemetry processes such as chassisd, rpd, or mib2d may crash and require a restart. This behavior can lead to significant outages, disrupting system operations until recovery is complete.

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Affected Version(s)

Junos OS 0 < 22.4R3-S8

Junos OS 23.2 < 23.2R2-S5

Junos OS 23.4 < 23.4R2

References

https://supportportal.juniper.net/JSA106021
vendor-advisory
https://kb.juniper.net/JSA106021
vendor-advisory

CVSS V4

Score:
7.1
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

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