What is the CVSS score of CVE-2026-21908?

CVE-2026-21908 has a CVSS 3.1 base score of 7.1 (High). CVSS vector: CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.0%.

Which versions of Junos are affected by CVE-2026-21908?

Organizations using A Use After Free vulnerability face moderate risk from CVE-2026-21908, a use-after-free vulnerability rated CVSS 7.1.

How to fix or mitigate CVE-2026-21908?

Within 7 days: Identify all affected systems and apply vendor patches promptly. If patching is delayed, consider network segmentation to limit exposure.

Junos CVE-2026-21908

HIGH

Use After Free (CWE-416)

2026-01-15 sirt@juniper.net

Juniper Use After Free Denial Of Service Junos Junos Os Evolved

7.1

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

7.1 HIGH

AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector

Adjacent

Attack Complexity

High

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

CVE Published

Jan 15, 2026 - 21:16 nvd

HIGH 7.1

DescriptionCVE.org

A Use After Free vulnerability was identified in the 802.1X authentication daemon (dot1xd) of Juniper Networks Junos OS and Junos OS Evolved that could allow an authenticated, network-adjacent attacker flapping a port to crash the dot1xd process, leading to a Denial of Service (DoS), or potentially execute arbitrary code within the context of the process running as root.

The issue is specific to the processing of a change in authorization (CoA) when a port bounce occurs. A pointer is freed but was then referenced later in the same code path. Successful exploitation is outside the attacker's direct control due to the specific timing of the two events required to execute the vulnerable code path.

This issue affects systems with 802.1X authentication port-based network access control (PNAC) enabled. This issue affects:

Junos OS:

from 23.2R2-S1 before 23.2R2-S5,
from 23.4R2 before 23.4R2-S6,
from 24.2 before 24.2R2-S3,
from 24.4 before 24.4R2-S1,
from 25.2 before 25.2R1-S2, 25.2R2;

Junos OS Evolved:

from 23.2R2-S1 before 23.2R2-S5-EVO,
from 23.4R2 before 23.4R2-S6-EVO,
from 24.2 before 24.2R2-S3-EVO,
from 24.4 before 24.4R2-S1-EVO,
from 25.2 before 25.2R1-S2-EVO, 25.2R2-EVO.

AnalysisAI

Juniper Junos OS and Junos OS Evolved contain a use-after-free vulnerability in the 802.1X authentication daemon that allows authenticated, network-adjacent attackers to crash the process or achieve arbitrary code execution as root by triggering specific port state changes. Exploitation requires precise timing of a change-of-authorization event during port transitions, making reliable exploitation difficult but possible. Systems with 802.1X port-based network access control enabled are affected, and no patch is currently available.

Technical ContextAI

Classified as CWE-416 (Use After Free). Affects Junos. A Use After Free vulnerability was identified in the 802.1X authentication daemon (dot1xd) of Juniper Networks Junos OS and Junos OS Evolved that could allow an authenticated, network-adjacent attacker flapping a port to crash the dot1xd process, leading to a Denial of Service (DoS), or potentially execute arbitrary code within the context of the process running as root.

The issue is specific to the processing of a change in authorization (CoA) when a port bounce occurs. A pointer is freed but