Exploited. On CISA's list since 2025-03-13.
Juniper Junos OS Improper Isolation or Compartmentalization Vulnerability
CVE-2025-21590 · Juniper Junos OS · Published 2025-03-12
How bad would it be?
6.7 out of 10
CVSS rates it medium.
How likely is it to be used?
1.7%
Estimated chance of exploitation in the next 30 days, higher than 77% of all scored flaws (EPSS, 2026-10-29).
Is it already being used?
Yes
CISA has seen it exploited in real attacks. For US government agencies the fix is deadline passed 575 days ago (2025-04-03).
What CISA says to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
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 the flaw is
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.
From the NVD.
Fixes and advisories
Learn this
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Understand the kind of weakness behind this flaw. These resources teach the weakness, rather than reproduce this specific CVE. Follow the vendor's advice above to fix the affected product.
CWE-653 · CISA KEV; NVD record: sirt@juniper.net. We have not selected a close learning match for this label.
CWE is a catalogue of weakness types. Labels come from the sources shown and can differ or change. Resource matches reviewed 16 October 2026.
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Exploited flaws from CISA's KEV catalogue. Chance of exploitation from EPSS by FIRST. Descriptions and scores from the NVD. This product uses the NVD API but is not endorsed or certified by the NVD.