Medium [CVE-2026-21921] Use After Free vulnerability in the chassis daemon (chassisd) of Juniper Networks Junos OS and Junos OS Evolved
This medium-severity Juniper Networks advisory covers CVE-2026-21921 affecting Junos, Junos OS, Junos OS Evolved.
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Summary
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:
- all versions before 22.4R3-S8,
- 23.2 versions before 23.2R2-S5,
- 23.4 versions before 23.4R2;
- all versions
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
- 22.4R3-S8
- 23.2R2-S5
- 23.4R2
- 22.4R3-S8-EVO
- 23.2R2-S5-EVO
- 23.4R2-EVO
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Mitigation
Upgrade to a fixed release: 22.4R3-S8, 23.2R2-S5, 23.4R2, 22.4R3-S8-EVO, 23.2R2-S5-EVO, 23.4R2-EVO. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
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