# Juniper Junos OS: Junos OS Improper Isolation or Compartmentalization Vulnerability · pwn.watch

> Juniper Junos OS contains an improper isolation or compartmentalization vulnerability. This vulnerability could allows a local attacker with high privileges to inject arbitrary code. Added to CISA KEV on 2025-03-13.

Page: https://pwn.watch/i/juniper-junos-os-cve-2025-21590 · generated 2026-10-22T20:45:43.249Z

## Status
- Severity: medium · status: closed · patch: patched
- Product: Juniper Junos OS
- Started: 2025-03-13 · closed: 2025-03-13
- CVEs: CVE-2025-21590
- Affected: See vendor advisory / CISA notes (versions not always listed in KEV feed)
- Fixed in: See vendor advisory linked in sources

## Follow this incident
- RSS (one item per update): https://pwn.watch/i/juniper-junos-os-cve-2025-21590/feed.xml
- JSON Feed: https://pwn.watch/i/juniper-junos-os-cve-2025-21590/feed.json
- Full data (timeline, sources, posts, agentBrief): https://pwn.watch/i/juniper-junos-os-cve-2025-21590.json
- This file: https://pwn.watch/i/juniper-junos-os-cve-2025-21590/llms.txt

## Updates (newest first)
- 2025-03-13: CISA added CVE-2025-21590 to the KEV catalog (due 2025-04-03).

## Fix brief
# Security brief: Juniper Junos OS: Junos OS Improper Isolation or Compartmentalization Vulnerability

Source: https://pwn.watch/i/juniper-junos-os-cve-2025-21590 · status: closed (closed Mar 13, 2025) · severity: medium · updated Mar 13, 2025

## Patch status
**PATCHED: fixed releases exist. Upgrade to a fixed version.**

## What it is
Juniper Junos OS contains an improper isolation or compartmentalization vulnerability. This vulnerability could allows a local attacker with high privileges to inject arbitrary code. Added to CISA KEV on 2025-03-13.

Severity detail: CVSS 4.4 (CNA, v3.1); actively exploited (CISA KEV)

- Product: Juniper Junos OS
- CVE / advisory ids: CVE-2025-21590

## Affected versions
- See vendor advisory / CISA notes (versions not always listed in KEV feed)

## Check whether you're affected
No generic command applies (the product is a hosted service, appliance or desktop app). Check the installed version in its admin UI / About screen and compare with the versions above.

## Fix
Upgrade to one of these fixed versions (or later on the same branch):
- See vendor advisory linked in sources

After upgrading, re-run the checks above and redeploy/restart the affected services.

## Latest updates
- Mar 13, 2025: CISA added CVE-2025-21590 to the KEV catalog (due 2025-04-03).

## Advisories
- [Juniper advisory: Juniper Junos OS](https://supportportal.juniper.net/s/article/2025-03-Out-of-Cycle-Security-Bulletin-Junos-OS-A-local-attacker-with-shell-access-can-execute-arbitrary-code-CVE-2025-21590?language=en_US) (Juniper)
- [NVD: CVE-2025-21590](https://nvd.nist.gov/vuln/detail/CVE-2025-21590) (NVD)
- [CISA Known Exploited Vulnerabilities Catalog](https://www.cisa.gov/known-exploited-vulnerabilities-catalog) (CISA)

## Caveats
Derived from CISA KEV JSON feed catalogVersion 2026.10.21. CVSS from the CVE record (cvelistV5). Exact affected/fixed version strings are not always in the KEV record; verify against the vendor advisory URL. startedAt uses dateAdded (exploitation may have begun earlier; many entries are older CVEs newly confirmed as exploited in 2025).

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Machine-readable: https://pwn.watch/i/juniper-junos-os-cve-2025-21590.json · all incidents: https://pwn.watch/incidents.json. Verify against the vendor advisory before changing production systems.