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

Source: https://junglewise.ai/threats/cve-2025-21590-juniper-junos-os-improper-isolation-or-compartmentalization  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-03-13. Updated: 2026-05-09  
License: CC BY 4.0 with a link back

CVE-2025-21590 · Severity: critical · CVSS 6.7 · Exploited in the wild · Published 2025-03-13

An improper isolation vulnerability in the Juniper Junos OS kernel allows a local attacker with high privileges and shell access to inject arbitrary code. The vulnerability cannot be exploited via the Junos CLI but can lead to a full compromise of device integrity.

Technologies: [Juniper Junos OS](https://junglewise.ai/threats/technologies/junos-os). Vendors: [Juniper](https://junglewise.ai/threats/vendors/juniper).

## Quick answers

**Is CVE-2025-21590 exploited in the wild?** Yes. CVE-2025-21590 is known to be exploited in the wild, first recorded on 13 March 2025. Treat it as urgent.

**How severe is CVE-2025-21590?** Critical severity, with a CVSS score of 6.7, published 13 March 2025.

**Which products and versions are affected?** Juniper Networks 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.

**Is there a fix for CVE-2025-21590?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2025-21590 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2025-21590?** Check whether you run Juniper Junos OS. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Juniper Networks 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

## Timeline

- 2025-03-12: disclosed: New CVE received from Juniper Networks
- 2025-03-13: kev added: Added to CISA Known Exploited Vulnerabilities Catalog
- 2025-03-13: exploited: Reported as exploited in the wild by CISA and Google Cloud/Mandiant blog

## Related threats

- [Juniper Junos OS EX Series PHP External Variable Modification Vulnerability](https://junglewise.ai/threats/cve-2023-36844-juniper-junos-os-ex-series-php-external-variable-modification)
- [Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability](https://junglewise.ai/threats/cve-2023-36846-juniper-junos-os-srx-series-missing-authentication-for-critical)
- [Juniper Junos OS EX Series and SRX Series PHP External Variable Modification Vulnerability](https://junglewise.ai/threats/cve-2023-36845-juniper-junos-os-ex-series-and-srx-series-php-external-variable)
- [Juniper Junos OS EX Series Missing Authentication for Critical Function Vulnerability](https://junglewise.ai/threats/cve-2023-36847-juniper-junos-os-ex-series-missing-authentication-for-critical)
- [Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability](https://junglewise.ai/threats/cve-2023-36851-juniper-junos-os-srx-series-missing-authentication-for-critical)