---
id: "CVE-2025-21590"
kind: "vulnerability"
aliases: ["CVE-2025-21590"]
title: "juniper junos: An Improper Isolation or Compartmentalization vulnerability in the kernel of Juniper Networks Junos OS allows a\u2026"
severity: "medium"
cvss: 6.7
epss: null
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Juniper Junos OS", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "juniper junos", "fixed": ["21.2"], "affected": "< 21.2", "ecosystem": "vendor"}, {"name": "juniper junos", "fixed": [], "affected": "= 21.2", "ecosystem": "vendor"}, {"name": "juniper junos", "fixed": [], "affected": "= 21.4", "ecosystem": "vendor"}, {"name": "juniper junos", "fixed": [], "affected": "= 22.2", "ecosystem": "vendor"}, {"name": "juniper junos", "fixed": [], "affected": "= 22.4", "ecosystem": "vendor"}, {"name": "juniper junos", "fixed": [], "affected": "= 23.2", "ecosystem": "vendor"}, {"name": "juniper junos", "fixed": [], "affected": "= 23.4", "ecosystem": "vendor"}, {"name": "juniper junos", "fixed": [], "affected": "= 24.2", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "infrastructure", "juniper", "junos", "network-gear"]
not_affected_if: ["not-running-junos"]
published_at: "2025-03-12T14:15:15+00:00"
first_seen_at: "2026-10-23T19:11:51+00:00"
updated_at: "2026-10-23T22:29:05+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2025-21590", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21590", "first_seen_at": "2026-10-23T22:29:05+00:00"}]
---

# juniper junos: An Improper Isolation or Compartmentalization vulnerability in the kernel of Juniper Networks Junos OS allows a…

Juniper Junos OS, the operating system on Juniper routers and switches, has an improper isolation flaw that lets a local attacker with high privileges inject arbitrary code. CISA lists it as actively exploited in the wild.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Juniper Junos OS affected ? fixed ?
- vendor:juniper junos affected < 21.2 fixed 21.2
- vendor:juniper junos affected = 21.2 fixed ?
- vendor:juniper junos affected = 21.4 fixed ?
- vendor:juniper junos affected = 22.2 fixed ?
- vendor:juniper junos affected = 22.4 fixed ?
- vendor:juniper junos affected = 23.2 fixed ?
- vendor:juniper junos affected = 23.4 fixed ?
- vendor:juniper junos affected = 24.2 fixed ?

## Fix

Apply mitigations per vendor instructions from Juniper; discontinue use of the product if mitigations are unavailable (per CISA required action).

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2025-21590
- 2026-10-23T22:29:05+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2025-21590

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_