Junos OS (SRX firewalls)
CVE-2026-21908: Use after free vulnerability In 802.1X authentication daemon can cause crash of the dot1xd process
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.
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Junos OS 23.2R2-S1 | 23.2R2-S5 or later |
| Junos OS 23.4R2 | 23.4R2-S6 or later |
| Junos OS 24.2 | 24.2R2-S3 or later |
| Junos OS 24.4 | 24.4R2-S1 or later |
| Junos OS 25.2 | 25.2R1-S2, 25.2R2 or later |
| Junos OS Evolved 23.2R2-S1 | 23.2R2-S5-EVO or later |
| Junos OS Evolved 23.4R2 | 23.4R2-S6-EVO or later |
| Junos OS Evolved 24.2 | 24.2R2-S3-EVO or later |
| Junos OS Evolved 24.4 | 24.4R2-S1-EVO or later |
| Junos OS Evolved 25.2 | 25.2R1-S2-EVO, 25.2R2-EVO or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
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.
Am I affected?
This issue requires support for 802.1X be enabled. For example:
[protocols dot1x authenticator ...]
Workarounds
There are no known workarounds for this issue.
Exploitation
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.