Junos
CVE-2026-21921
MEDIUM
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
2DescriptionCVE.org
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.
AnalysisAI
Repeated telemetry collector subscriptions in Juniper Junos OS and Junos OS Evolved trigger a use-after-free vulnerability in the chassis daemon, allowing authenticated network attackers to crash critical processes and cause denial of service. Affected versions prior to 22.4R3-S8, 23.2R2-S5, and 23.4R2 are vulnerable when telemetry-capable daemons experience continuous sensor subscription cycles. No patch is currently available, leaving affected systems exposed until updates are released.
Technical ContextAI
Classified as CWE-416 (Use After Free). Affects Junos. 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
RemediationAI
Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.
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Same weakness CWE-416 – Use After Free
View allSame technique Use After Free
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External POC / Exploit Code
Leaving vuln.today