What is the CVSS score of CVE-2026-21902?

CVE-2026-21902 has a CVSS 4.0 base score of 9.3 (Critical). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:L/AU:Y/R:U/RE:M/U:Red. EPSS exploitation probability: 0.3%.

How to fix or mitigate CVE-2026-21902?

Within 24 hours: Inventory all PTX Series devices in production and assess network exposure to untrusted sources; implement emergency network segmentation to restrict access to affected devices. Within 7 days: Deploy compensating controls (network ACLs, firewall rules) to block external access to the On-Box Anomaly detection framework; coordinate with Juniper for patch timeline and testing procedures. Within 30 days: Apply vendor patch immediately upon availability; conduct full security audit of affected devices for signs of compromise.

Juniper CVE-2026-21902

CRITICAL

Incorrect Permission Assignment for Critical Resource (CWE-732)

2026-02-25 sirt@juniper.net

Information Disclosure Juniper

9.3

CVSS 4.0 · NVD

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Network access to exposed anomaly detection service
Exploit

Send malicious request to service
Execution

Execute arbitrary code as root
Impact

Gain complete device control

Vulnerability Assessment

Weakness	CWE CWE-732 OWASP Top 10:2025 A01:2025 - Broken Access Control ASVS 5.0 V13 - Configuration Permission assignment review
Exploitation Conditions	On-Box Anomaly detection framework enabled by default on Juniper Junos OS Evolved PTX Series with service exposed on externally accessible port instead of restricted internal routing instance only.
Impact	CVSS 9.8, EPSS 0.28%. Attackers can disable anomaly detection to avoid triggering alerts during exploitation of other vulnerabilities.
Exploit ScenarioDerived	Attacker with initial access modifies anomaly detection configuration to disable monitoring, then performs further attacks without triggering security alerts.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Incorrect permission assignment on critical resources in Juniper Networks On-Box Anomaly detection framework. Allows unauthorized modification of anomaly detection configuration, potentially disabling security monitoring.

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 21:55 CVSS 9.3

Permission misconfiguration in Juniper On-Box Anomaly detection.

RemediationAI

Apply Juniper security update. Verify file permissions on anomaly detection configuration.

Affects your stack

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Technical ContextAI · show details

CWE-732 incorrect permission assignment for critical resource. The anomaly detection framework's configuration files have incorrect permissions allowing unauthorized modification.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.3 CRITICAL

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:L/AU:Y/R:U/RE:M/U:Red

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Attack Requirements

None

Privileges Required

None

User Interaction

None

Vulnerable system: Confidentiality

High

Vulnerable system: Integrity

High

Vulnerable system: Availability

High

Subsequent system: Confidentiality

None

Subsequent system: Integrity

None

Subsequent system: Availability

Low

DescriptionCVE.org

An Incorrect Permission Assignment for Critical Resource vulnerability in the On-Box Anomaly detection framework of Juniper Networks Junos OS Evolved on PTX Series allows an unauthenticated, network-based attacker to execute code as root.

The On-Box Anomaly detection framework should only be reachable by other internal processes over the internal routing instance, but not over an externally exposed port. With the ability to access and manipulate the service to execute code as root a remote attacker can take complete control of the device. Please note that this service is enabled by default as no specific configuration is required.

This issue affects Junos OS Evolved on PTX Series:

25.4 versions before 25.4R1-S1-EVO, 25.4R2-EVO.

This issue does not affect Junos OS Evolved versions before 25.4R1-EVO.

This issue does not affect Junos OS.

Articles & Coverage 1

labs.watchtowr.com Juniper PTX Series Unauthenticated RCE via CVE-2026-21902 On-Box Anomaly Detection

Executive ViewAI

Why It Matters

A critical vulnerability in Juniper PTX Series routers allows unauthenticated attackers to execute code with root privileges, potentially compromising core network infrastructure and all connected systems. Organizations operating PTX Series devices are at immediate risk of complete network takeover, data exfiltration, and service disruption.

Business Impact: Severe

Compensating Controls

Implement network ACLs and firewall rules to block external/untrusted access to internal routing instance ports used by On-Box Anomaly detection framework; disable the On-Box Anomaly detection feature if operationally feasible until patch is available; restrict network access to PTX Series management interfaces; increase monitoring and logging for anomaly detection service activity; segment PTX Series devices behind firewall boundaries with strict ingress filtering.

Threat Intelligence Overview

EPSS Score

0.3%

Top 49% exploitable

Data Quality

4 sources

Confidence: Medium

NVD

CVE.org

EPSS

GitHub

VulDB

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 CRITICAL

CISA KEV No

Public POC No

EPSS 0.3%

Patch available No

Active threat No

Deciding rule

CRITICAL severity

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

None

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact

Very High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +46

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.