NVD / CVE Program· CNA juniper

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

Noroxi assessment

Priority: Monitor (action score 30/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.31% (FIRST EPSS).
Someone on the same network segment can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Juniper Networks Junos OS 23.2R2-S5, 23.4R2-S6, 24.2R2-S3; Juniper Networks Junos OS Evolved 23.2R2-S5-EVO, 23.4R2-S6-EVO, 24.2R2-S3-EVO.

Low priority for now. Upgrade to Juniper Networks Junos OS 23.2R2-S5, 23.4R2-S6, 24.2R2-S3; Juniper Networks Junos OS Evolved 23.2R2-S5-EVO, 23.4R2-S6-EVO, 24.2R2-S3-EVO or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.5 · v4.0—No exploit Fix available

Published: Jan 15, 2026
Updated: Jun 17, 2026
EPSS: 0.3% · 24th percentile
CWE: CWE-416

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.3%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · juniper: 7.1; NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
juniper	junos	cpe:2.3:o:juniper:junos
juniper	junos os evolved	cpe:2.3:o:juniper:junos_os_evolved

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

juniper junos23.2
juniper junos23.4
juniper junos24.2
juniper junos24.4
juniper junos25.2
juniper junos os evolved23.2
juniper junos os evolved23.4
juniper junos os evolved24.2
juniper junos os evolved24.4
juniper junos os evolved25.2

Versions reported by the vendor

Affected version ranges reported by the assigning authority (juniper). Independent of NVD's CPE analysis and usually ahead of it.

Juniper Networks Junos OS
- 23.2R2-S1 and later · before 23.2R2-S5affected · semver
- 23.4R2 and later · before 23.4R2-S6affected · semver
- 24.2 and later · before 24.2R2-S3affected · semver
- 24.4 and later · before 24.4R2-S1affected · semver
- 25.2 and later · before 25.2R1-S2, 25.2R2affected · semver
Juniper Networks Junos OS Evolved
- 23.2R2-S1 and later · before 23.2R2-S5-EVOaffected · semver
- 23.4R2 and later · before 23.4R2-S6-EVOaffected · semver
- 24.2 and later · before 24.2R2-S3-EVOaffected · semver
- 24.4 and later · before 24.4R2-S1-EVOaffected · semver
- 25.2 and later · before 25.2R1-S2-EVO, 25.2R2-EVOaffected · semver

Same product

juniper: all records

Other highest-scoring records for the same primary product.

CVE-2023-36845Junos OS: EX and SRX Series: A PHP vulnerability in J-Web allows an unauthenticated to control an important environment variableKEV
98Now
CVE-2023-36846Junos OS: SRX Series: A vulnerability in J-Web allows an unauthenticated attacker to upload arbitrary filesKEV
79This week
CVE-2023-36844Junos OS: EX Series: A PHP vulnerability in J-Web allows an unauthenticated attacker to control important environment variablesKEV
78This week

Published before and after this one in the same product

← EarlierCVE-2026-21905Jan 15, 2026 · Junos OS: SRX Series, MX Series with MX-SPC3 or MS-MPC: Receipt of multiple specific SIP messages results in flow management process crash
34Monitor
← EarlierCVE-2026-21906Jan 15, 2026 · Junos OS: SRX Series: With GRE performance acceleration enabled, receipt of a specific ICMP packet causes the PFE to crash
34Monitor
Later →CVE-2026-21909Jan 15, 2026 · Junos OS and Junos OS Evolved: Receipt of specific IS-IS update packet causes memory leak leading to RPD crash
28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Juniper Networks Junos OS	23.2R2-S5	Vendor (CNA)
Juniper Networks Junos OS	23.4R2-S6	Vendor (CNA)
Juniper Networks Junos OS	24.2R2-S3	Vendor (CNA)
Juniper Networks Junos OS	24.4R2-S1	Vendor (CNA)
Juniper Networks Junos OS	25.2R1-S2, 25.2R2	Vendor (CNA)
Juniper Networks Junos OS Evolved	23.2R2-S5-EVO	Vendor (CNA)
Juniper Networks Junos OS Evolved	23.4R2-S6-EVO	Vendor (CNA)
Juniper Networks Junos OS Evolved	24.2R2-S3-EVO	Vendor (CNA)
Juniper Networks Junos OS Evolved	24.4R2-S1-EVO	Vendor (CNA)
Juniper Networks Junos OS Evolved	25.2R1-S2-EVO, 25.2R2-EVO	Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2025-52946188 days apartJunos OS and Junos OS Evolved: With traceoptions enabled, receipt of malformed AS PATH causes RPD crash
34Monitor
CVE-2026-219210 days apartJunos OS and Junos OS Evolved: When telemetry collectors are frequently subscribing and unsubscribing to sensors chassisd or rpd will crash
28Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

CVE-2025-3065083 days apartJunos OS: Privileged local user can gain access to a Linux-based FPC as root
33Monitor
CVE-2025-5998098 days apartJunos OS: When a user with the name ftp or anonymous is configured unauthenticated filesystem access is allowed
27Monitor

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Someone on the same network segment can trigger it.
A low-privileged account is enough.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Adjacent
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: X

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

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

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

Fix✗ → ✓Sep 28, 2026, 10:11 PM UTC

For records you follow, these changes also arrive as notifications. →

References

kb.juniper.net/JSA106007

Show all references (1 more)

supportportal.juniper.net/JSA106007

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records