CVE-2026-21908
Junos OS and Junos OS Evolved: 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.
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.
Attack profile
How easy it is to exploit
- Attack vector
- Adjacent network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Junos OS and Junos OS Evolved: 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.
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.
- Record
CVE-2026-21908- CVSS 4.0
- 7.5 High
CVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:L/RE:M/U:Green - CVSS 3.1
- 7.1 High
CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
EUVDEUVD-2026-2690
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.
- Record
EUVD-2026-2690- CVSS 4.0
- 7.5 High
CVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:L/RE:M/U:Green - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-h976-gqwv-338w
A Use After Free vulnerability was identified in the 802.1X authentication daemon (dot1xd) of...
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.
- Record
GHSA-h976-gqwv-338w- CVSS 4.0
- 7.5 High
CVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:M/U:Green - CVSS 3.1
- 7.1 High
CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-21908- CVSS 4.0
- 7.5 High
CVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:M/U:Green - CVSS 3.1
- 7.1 High
CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-21908 is a high vulnerability (CVSS 7.5) in Juniper Junos, published January 15, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.31%, the 24th percentile. No source names a fixed version.