SB2026012020 - Use-after-free in Junos OS Evolved and Juniper Junos OS
Published: January 20, 2026
Security Bulletin ID
SB2026012020
Severity
Medium
Patch available
YES
Number of vulnerabilities
1
Exploitation vector
Remote access
Highest impact
Denial of service
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 1 security vulnerability.
1) Use-after-free (CVE-ID: CVE-2026-21921)
The vulnerability allows a remote user to perform a denial of service (DoS) attack.
The vulnerability exists due to use after free error in the chassis daemon (chassisd). A remote user can 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.
Remediation
Install update from vendor's website.