Instituto Nacional de ciberseguridad. Sección Incibe
Instituto Nacional de Ciberseguridad. Sección INCIBE-CERT

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CVE-2026-21921

Severity CVSS v4.0:
HIGH
Type:
CWE-416 Use After Free
Publication date:
15/01/2026
Last modified:
23/01/2026

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).<br /> <br /> 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.<br /> <br /> This issue affects:<br /> <br />  Junos OS: <br /> <br /> <br /> <br /> * all versions before 22.4R3-S8,<br /> * 23.2 versions before 23.2R2-S5,<br /> * 23.4 versions before 23.4R2;<br /> <br /> <br /> <br /> <br /> Junos OS Evolved:<br /> <br /> <br /> <br /> * all versions before 22.4R3-S8-EVO,<br /> * 23.2 versions before 23.2R2-S5-EVO,<br /> * 23.4 versions before 23.4R2-EVO.

Impact

Vector 4.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:A/RE:M CVSS v4.0 Severity and Metrics:

Base Score: 7.10 HIGH
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:A/RE:M

Attack Vector (AV): Network
Attack Complexity (AC): Low
Attack Requirements (AT): None
Privileges Required (PR): Low
User Interaction (UI): None
Confidentiality (VC): None
Integrity (VI): None
Availability (VA): High
Confidentiality (SC): None
Integrity (SI): None
Availability (SA): Low
Automatable (AU): Yes
Recovery (R): Automatic
Vulnerability Response Effort (RE): Moderate

Base Score 4.0
7.10
Severity 4.0
HIGH
Vector 3.x
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CVSS v3.1 Severity and Metrics:

Base Score: 6.50 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): Low
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): None
Integrity (I): None
Availability (A): High

Base Score 3.x
6.50
Severity 3.x
MEDIUM

Vulnerable products and versions

CPE From Up to
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:* 22.4 (excluding)
cpe:2.3:o:juniper:junos:22.4:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r3-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r3-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r3-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r3-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r3-s5:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r3-s6:*:*:*:*:*:*

To consult the complete list of CPE names with products and versions, see this page


References to Advisories, Solutions, and Tools