Product:
Junos OS
Summary
A Use After Free vulnerability in the chassis daemon of Junos OS allows a network-based attacker authenticated with low privileges to cause a Denial-of-Service. When telemetry collectors frequently subscribe and unsubscribe to sensors over a long period, processes like chassisd can crash and restart, potentially leading to a complete outage until recovery.
Details
| Severity | Base Score | CVE |
|---|---|---|
| HIGH | 7.1 | CVE-2026-21921 |
Exploitation
To exploit this vulnerability, an attacker with low privileges can continuously subscribe and unsubscribe telemetry collectors to sensors. This repeated action can overwhelm the chassisd process, causing it to crash and restart, which may result in a Denial-of-Service condition affecting the network.
Affected Products
- 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.
Mitigation
To mitigate this vulnerability, it is recommended to upgrade to the latest versions of Junos OS and Junos OS Evolved that are not affected by this issue. Regular monitoring and management of telemetry subscriptions can also help prevent potential exploitation.