Juniper Junos OS up to 25.4R0 symlink

CVSS Meta Temp Score
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CTI Interest Score
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6.9$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as critical, has been found in Juniper Junos OS up to 25.4R0. Impacted is an unknown function. The manipulation leads to symlink. This vulnerability is referenced as CVE-2026-21916. The attack can only be performed from a local environment. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Juniper Junos OS up to 25.4R0. This issue affects an unknown functionality. The manipulation with an unknown input leads to a symlink vulnerability. Using CWE to declare the problem leads to CWE-61. The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

A UNIX Symbolic Link (Symlink) Following vulnerability in the CLI of Juniper Networks Junos OS allows a local, authenticated attacker with low privileges to escalate their privileges to root which will lead to a complete compromise of the system. When after a user has performed a specific 'file link ...' CLI operation, another user commits (unrelated configuration changes), the first user can login as root. This issue affects Junos OS: * all versions before 23.2R2-S7, * 23.4 versions before 23.4R2-S6, * 24.2 versions before 24.2R2-S3, * 24.4 versions before 24.4R2-S2, * 25.2 versions before 25.2R2. This issue does not affect versions 25.4R1 or later.

It is possible to read the advisory at kb.juniper.net. The identification of this vulnerability is CVE-2026-21916 since 01/05/2026. The exploitation is known to be easy. Attacking locally is a requirement. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 04/13/2026).

The vulnerability scanner Nessus provides a plugin with the ID 305598 (Juniper Junos OS Vulnerability (JSA107807)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 23.2R2-S7, 23.4R2-S6, 24.2R2-S3, 24.4R2-S2, 25.2R2 or 25.4R1 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (305598). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 7.0
VulDB Meta Temp Score: 6.9

VulDB Base Score: 6.8
VulDB Temp Score: 6.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.3
CNA Vector (juniper): 🔒

CVSSv2info

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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Symlink
CWE: CWE-61 / CWE-59
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 305598
Nessus Name: Juniper Junos OS Vulnerability (JSA107807)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Junos OS 23.2R2-S7/23.4R2-S6/24.2R2-S3/24.4R2-S2/25.2R2/25.4R1

Timelineinfo

01/05/2026 CVE reserved
04/10/2026 +94 days Advisory disclosed
04/10/2026 +0 days VulDB entry created
04/13/2026 +3 days VulDB entry last update

Sourcesinfo

Vendor: juniper.net

Advisory: JSA107807
Status: Confirmed

CVE: CVE-2026-21916 (🔒)
GCVE (CVE): GCVE-0-2026-21916
GCVE (VulDB): GCVE-100-356735

Entryinfo

Created: 04/10/2026 06:31
Updated: 04/13/2026 18:57
Changes: 04/10/2026 06:31 (80), 04/13/2026 18:57 (2)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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