Log in Start free

Vulnerability · Published Jan 15, 2026 · Assigned by juniper

CVE-2026-21921Junos OS and Junos OS Evolved: When telemetry collectors are frequently subscribing and unsubscribing to sensors chassisd or rpd will crash

Medium 6.5

In plain English

A medium-severity use-after-free in Junos OS from Juniper Networks. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.4%top 68.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
Juniper Networks Junos OS 0 – before 22.4R3-S823.2 – before 23.2R2-S523.4 – before 23.4R2
Juniper Networks Junos OS Evolved 0 – before 22.4R3-S8-EVO23.2 – before 23.2R2-S5-EVO23.4 – before 23.4R2-EVO

Weakness: CWE-416 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

References