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Fencer Intel
medium 4.4

CVE-2025-21590 kev in the critical feed json

Junos OS: An local attacker with shell access can execute arbitrary code

published last yr. modified last mo. also EUVD-2025-6303

cvss
4.4
version 3.1, CNA
cisa kev
Exploited
added 2025-03-13
epss
1.7%
EPSS 1.7% chance of exploitation in 30 days, percentile 78%
public exploits
0
none known

Summary

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.

Patch / fix

cisa required action 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 Networks Junos OS 21.2R3-S9, 21.4R3-S10, 22.2R3-S6, 22.4R3-S6, 23.2R2-S3, 23.4R2-S4, 24.2R1-S2, 24.2R2

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Timeline

  1. Published
  2. Added to CISA KEV
  3. CISA SSVC: exploitation active
  4. CISA patch deadline

Known exploited

Added
last yr.
Patch by
2025-04-03 (last yr.)
Ransomware
Not known
Required action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Vendor, product
Juniper, Junos OS
CISA name
Juniper Junos OS Improper Isolation or Compartmentalization Vulnerability

ATT&CK techniques

How it is exploited and what it leads to, in MITRE ATT&CK terms.

  • T1068 Exploitation for Privilege Escalation exploitation
  • T1059 Command and Scripting Interpreter primary impact

kev release 2025-07-28, att&ck v16.1. KEV to ATT&CK mappings by the MITRE Center for Threat-Informed Defense (Mappings Explorer, Apache-2.0). © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. Terms of use

CISA SSVC

Exploitation
Active, exploited in the wild
Automatable
no
Technical impact
total
Assessed
last yr.

Exploit prediction

1.75% chance of exploitation in the next 30 days, higher than 78% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 4.4 CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
CNA 4.0 6.7 CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
CNA 4.0 6.7 CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • Juniper Networks Junos OS

Classification

Weakness
  • CWE-653 Improper Isolation or Compartmentalization

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.