CVE-2025-21590
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.
do firstApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Can a WAF block it? No. The attack needs local access to the machine, so a WAF is not on its path.
Also consider: patch
Based on the attack vector (local or physical access). We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2025-21590 being exploited?
Yes. CVE-2025-21590 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2025-21590?
CVE-2025-21590 is rated Medium with a CVSS score of 4.4. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2025-21590?
Yes. A fix has been recorded for CVE-2025-21590. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2025-21590 affect?
CVE-2025-21590 affects juniper:junos. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
- affected< 21.2R3-S9
- affected>= 21.4 and < 21.4R3-S10
- affected>= 22.2 and < 22.2R3-S6
- affected>= 22.4 and < 22.4R3-S6
- affected>= 23.2 and < 23.2R2-S3
- affected>= 23.4 and < 23.4R2-S4
- affected>= 24.2 and < 24.2R1-S2, 24.2R2
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
cisa ssvc
- exploitation
- active
- automatable
- no
- technical impact
- total
Assessed by CISA 14 Mar 2025 (SSVC 2.0.3).
timeline
- 12 Mar 2025Published
- 13 Mar 2025Added to CISA KEV (exploited in the wild) · same day later
- 14 Mar 2025CISA SSVC assessment: exploitation active · 1 day later
- 3 Apr 2025CISA remediation due date (US federal agencies) · 20 days later
- 26 Feb 2026CVE record last updated · 330 days (about 11 months) later
- 2 Nov 2026Analysed by vulneraibility.com · 249 days (about 8 months) later
- Advisorysupportportal.juniper.net /JSA93446
- Advisorycloud.google.com /blog/topics/threat-intelligence/china-nexus-espionage-targets-juniper-routers
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-21590
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.