How severe is CVE-2025-21590?

CVE-2025-21590 has a CVSS score of 4.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2025-21590?

Affected package information for CVE-2025-21590 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2025-21590?

No fixed version has been published for CVE-2025-21590 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2025-21590 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-21590 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-21590?

CVE-2025-21590 has an EPSS (Exploit Prediction Scoring System) score of 1.7%, placing it in the 83th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

Is CVE-2025-21590 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2025-21590 (Juniper Junos OS Improper Isolation or Compartmentalization Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2025-03-13. CISA required all US federal civilian agencies to remediate this vulnerability by 2025-04-03. The required action was: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2025-21590?

CVE-2025-21590 is classified as CWE-653 (CWE-653). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Which products and versions are affected by CVE-2025-21590?

CVE-2025-21590 affects juniper junos (7 versions, e.g. 21.2, 21.4, 22.2…). Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2025-21590 published, and has it been updated?

CVE-2025-21590 was published on March 12, 2025 and was last updated on October 24, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2025-03-13 — agencies required to remediate by 2025-04-03

CVE-2025-21590

MEDIUM

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…

Published

Mar 12, 2025

Updated

Oct 24, 2025

Affected

0 pkgs

Patched

None yet

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

1.7%probability of exploitation in next 30 days

Lower Risk83th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

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.

Affected Products

1 product · 82 configurations

junosjuniper

≤ 21.2

7 versions

21.221.422.222.423.223.424.2

Frequently Asked Questions

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 b

O3 Security · Impact-Aware SCA

Is CVE-2025-21590 in your stack?

O3 detects CVE-2025-21590 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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