Medium severity · published Jan 15, 2026
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 with low privileges…
6.5
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 31% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
JO
Junos OS · Juniper
before 22.4; 22.4; 22.4; 22.4; 22.4; 22.4; +23 more · source: NVD
JO
Junos OS Evolved · Juniper
before 22.4; 22.4; 22.4; 22.4; 22.4; 22.4; +23 more · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-21921
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-21921
Vendor Advisory
https://kb.juniper.net/JSA106021
Vendor Advisory
https://supportportal.juniper.net/JSA106021
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