CVE intelligence and bounded remediation

CVE-2026-21908 — Juniper Junos security vulnerability

High CVSS 7.5

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, 2…

Severity
High
CVSS
7.5 (4.0)
Published
2026-01-15
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-416

Affected products

  • juniper / junos / 23.2
  • juniper / junos / 23.4
  • juniper / junos / 24.2

Showing 3 representative product identities from 51 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Use-after-free, double free, and expired resource use

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Trace ownership, references, callbacks, asynchronous tasks, and teardown paths around the affected object or resource.
  • Identify reachable inputs and timing or state transitions that can release the object while references remain.
  • Confirm affected builds, allocators, feature flags, architectures, and process privileges.

Remediate safely

  • Apply the maintained ownership or lifetime fix and rebuild all artifacts containing the affected native code.
  • Use explicit ownership, safe reference management, cancellation and join semantics, and idempotent teardown.
  • Add deterministic lifetime tests plus isolated sanitizer and concurrency coverage for shutdown and error paths.

Authoritative sources

Complete CVE record and remediation plan

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