What’s Vulnerable › Vulnerabilities

CVE-2025-21590: Juniper Junos OS Improper Isolation or Compartmentalization Vulnerability

• Severity: medium (CVSS 4.4 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2025-03-13
• EPSS: 1.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-03-12 · updated 2026-10-01
• Weakness: CWE-653

Description

An Improper Isolation or Compartmentalization vulnerability in the kernel of Juniper Networks Junos OS allows a local attacker with high privileges to compromise the integrity of the device. A local attacker with access to the shell is able to inject arbitrary code which can compromise an affected device. This issue is not exploitable from the Junos CLI. This issue affects Junos OS:  * All versions before 21.2R3-S9, * 21.4 versions before 21.4R3-S10,  * 22.2 versions before 22.2R3-S6,  * 22.4 versions before 22.4R3-S6,  * 23.2 versions before 23.2R2-S3,  * 23.4 versions before 23.4R2-S4, * 24.2 versions before 24.2R1-S2, 24.2R2.

Summary

CVE-2025-21590 is an improper isolation or compartmentalization flaw in the Juniper Junos OS kernel that lets a local attacker with shell access and high privileges inject arbitrary code and compromise device integrity. It cannot be exploited from the Junos CLI. It affects Junos OS releases before 21.2R3-S9, 21.4R3-S10, 22.2R3-S6, 22.4R3-S6, 23.2R2-S3, 23.4R2-S4, and 24.2R1-S2/24.2R2. The flaw is listed in CISA's Known Exploited Vulnerabilities catalog with active exploitation, so apply the vendor's fixed releases or mitigations promptly, or discontinue use if none are available.

CVE-2025-21590 ثغرة ضعف في العزل أو التقسيم داخل نواة Juniper Junos OS تتيح لمهاجم محلي يملك وصولاً إلى الـ shell وامتيازات عالية حقن تعليمات برمجية عشوائية والإضرار بسلامة الجهاز، ولا يمكن استغلالها من واجهة Junos CLI. تؤثر في إصدارات Junos OS السابقة لـ 21.2R3-S9 و21.4R3-S10 و22.2R3-S6 و22.4R3-S6 و23.2R2-S3 و23.4R2-S4 و24.2R1-S2/24.2R2. الثغرة مدرجة في كتالوج CISA للثغرات المعروفة الاستغلال مع استغلال نشط، لذا يجب تطبيق الإصدارات المُصلحة أو التخفيفات من المورّد فوراً، أو إيقاف استخدام المنتج إن لم تتوفر معالجات.

Affected products

• Juniper Junos OS: before 21.2; 21.2, 21.2-r1, 21.2-r1-s1, 21.2-r1-s2, 21.2-r2, 21.2-r2-s1 (+72) — fixed in 21.2

How to fix

Upgrade to a fixed version: Juniper Junos OS 21.2. Check the vendor advisory for mitigations.

References

• https://cloud.google.com/blog/topics/threat-intelligence/china-nexus-espionage-targets-juniper-routers
• https://supportportal.juniper.net/JSA93446
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-21590

Get alerted when CVE-2025-21590 or the next vulnerability affects your stack