Exploited vulnerability · CISA KEV

Is CVE-2025-21590 exploited? Yes: in CISA KEV since 13 Mar 2025

Gociux · Juniper Junos OS · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2025-21590, Juniper Junos OS Improper Isolation or Compartmentalization Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 13 Mar 2025, 1 days after it was published. It affects Juniper Junos OS, an internet-facing product of the kind attackers use for initial access. If you run it, CISA's required action is: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

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.

What to do

1. Check whether you run it. Look for Junos OS in your asset inventory, including appliances and cloud images. Stack check lists every exploited Juniper CVE at once.
2. Apply the fix. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 12 Mar 2025.
4. Get told next time. Email alerts when CISA adds a CVE for Juniper.

Other exploited CVEs in Junos OS

• CVE-2023-36844: Juniper Junos OS EX Series PHP External Variable Modification Vulnerability (13 Nov 2023)
• CVE-2023-36845: Juniper Junos OS EX Series and SRX Series PHP External Variable Modification Vulnerability (13 Nov 2023)
• CVE-2023-36846: Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability (13 Nov 2023)
• CVE-2023-36847: Juniper Junos OS EX Series Missing Authentication for Critical Function Vulnerability (13 Nov 2023)
• CVE-2023-36851: Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability (13 Nov 2023)
• CVE-2020-1631: Juniper Junos OS Path Traversal Vulnerability (25 Mar 2022)

References

• supportportal.juniper.net/s/article/2025-03-Out-of-Cycle-Security-Bulletin-Junos-OS-A
• nvd.nist.gov/vuln/detail/CVE-2025-21590

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in March 2025 · Juniper scorecard · act-now radar.