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Junos CVE-2025-21590

MEDIUM
Improper Isolation or Compartmentalization (CWE-653)
2025-03-12 sirt@juniper.net
RCE Juniper Junos
6.7
CVSS 4.0 · Vendor: juniper
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Vulnerability Assessment

Weakness
CWE
CWE-653
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V14 - Configuration Dependency management, component inventory
Impact

CVSS 6.7. EPSS 0.9%. KEV-listed (actively exploited in the wild). No patch confirmed.
Exploit ScenarioDerived

An attacker could exploit this vulnerability in An Improper to compromise the security of affected deployments, potentially impacting confidentiality, integrity, or availability.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Exploited in the wild (CISA KEV) No patch listed yet 0.9% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 26, 2026

A security vulnerability in An Improper (CVSS 6.7) that allows a local attacker with high privileges. Risk factors: actively exploited (KEV-listed).

Earlier versions of this analysis (1)
v1 Mar 26, 2026 - 11:20 CVSS 6.7

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 a

RemediationAI

Monitor vendor channels for patch availability. This is CISA KEV-listed — federal agencies must remediate per BOD 22-01 deadlines.

Affects your stack

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Technical ContextAI · show details

Vulnerability type not specified by vendor. Affects An Improper.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

Vendor (juniper) PRIMARY 6.7 MEDIUM
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

Primary rating from Vendor (juniper) · only source for this CVE.

CVSS VectorVendor: juniper

Attack Vector
Local
Attack Complexity
Low
Attack Requirements
None
Privileges Required
High
User Interaction
None
Vulnerable system: Confidentiality
None
Vulnerable system: Integrity
High
Vulnerable system: Availability
None
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

Lifecycle Timeline

2
Added to CISA KEV
Oct 24, 2025 - 16:44 cisa
CISA KEV
CVE Published
Mar 12, 2025 - 14:15 nvd
MEDIUM 6.7

DescriptionCVE.org

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.

Executive ViewAI

Why It Matters

Organizations using An Improper should be aware of notable risk from CVE-2025-21590 rated CVSS 6.7. Exploitation could compromise the security of affected deployments. This vulnerability is actively exploited in the wild (KEV-listed). Organizations should apply vendor updates when available and monitor for exploitation.

Business Impact: High
Compensating Controls

Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.

Threat Intelligence Overview

Threat Score
4.9/10
Composite threat intelligence
EPSS Score
0.9%
Top 25% exploitable
Threat Intel
2
1 source
Data Quality
5 sources
Confidence: Medium
NVD CVE.org CISA KEV EPSS THREAT

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV Yes
Public POC No
EPSS 0.9%
Patch available No
Active threat Yes
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Out-of-Cycle
Exploitation· derived
Active
System Exposure· derived
Small
Automatable· derived
No
Human Impact
High

Priority Score

95
Low Medium High Critical
KEV: +50
EPSS: +1
CVSS: +34
PoC: 0
Weaponized: 0
Threat intel: +10
Gov advisory: 0

Attack Technique

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)CVE.org

cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s5:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s6:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s7:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s8:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r1-s1:*:*:*:*:*:*
+ 59 more

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Threat IntelligenceMISP

ATT&CK Techniques (observed)
T1203 - Exploitation for Client Execution T1055 - Process Injection
Sources: MITRE ATT&CK

References

Advisories & patches
ADVISORY https://supportportal.juniper.net/JSA93446 REF https://cloud.google.com/blog/topics/threat-intelligence/china-nexus-espionage-targets-juniper-routers REF https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-21590

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