dbcve.org
Junos Os EvolvedOperating system · Juniper

CVE-2026-21902

CRITICAL · 9.8 CVSS v3.1 Published 2026-02-25
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

An incorrect permission assignment in the On-Box Anomaly detection framework of Junos OS Evolved on PTX Series exposes an internal service that should only be reachable via the internal routing instance over an externally accessible network port. This allows unauthenticated, network-based attackers to execute arbitrary code as root, achieving full device compromise.

MitigationApply Juniper patch 25.4R1-S1-EVO or later; if patching is immediately infeasible, disable the On-Box Anomaly detection service via configuration and restrict network access to the management plane.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Junos Os EvolvedOperating system
Affected:= 25.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm device is PTX series running Junos OS Evolved
    Run 'show version' or 'show chassis hardware' to identify the device model and verify it is a PTX Series running Junos OS Evolved
    Affected if Device is not a PTX Series or is not running Junos OS Evolved (vulnerability only applies to this combination)
  2. Check installed Junos OS Evolved version
    Run 'show version' and examine the Junos OS Evolved version number; compare against the affected version 25.4
    Affected if Version is exactly 25.4 (this is the only version listed as affected)
  3. Verify On-Box Anomaly detection service status
    Run 'show configuration services anomaly-detection' or 'show configuration | match anomaly-detection' to check if the On-Box Anomaly detection service is enabled in the configuration
    Affected if On-Box Anomaly detection is enabled (the vulnerability exploits this service)

User is affected if the device is a PTX Series running Junos OS Evolved version 25.4 with On-Box Anomaly detection service enabled, exposing an internal service on an externally accessible port.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Juniper patch 25.4R1-S1-EVO or later; if patching is immediately infeasible, disable the On-Box Anomaly detection service via configuration and restrict network access to the management plane.

Recommended fix High confidence

25.4R1-S1-EVO or 25.4R2-EVO (or later stable release)

  1. 1. Identify current Junos OS Evolved version on PTX Series device using 'show version' command
  2. 2. Confirm the device is running a vulnerable version (25.4 before 25.4R1-S1-EVO or 25.4R1-EVO through 25.4R1 but not including S1)
  3. 3. Schedule maintenance window for upgrade (this is a critical unauthenticated remote code execution vulnerability)
  4. 4. Download the fixed release: either 25.4R1-S1-EVO or 25.4R2-EVO (or later) from Juniper Networks support portal
  5. 5. Upload the Junos OS Evolved package to the device using 'request system software add' command
  6. 6. Reboot the device using 'request system reboot' command
  7. 7. After reboot, verify the new version is installed using 'show version'
  8. 8. Confirm the On-Box Anomaly detection framework is no longer exposed on external ports by verifying internal-only binding
Caveat Standard Junos OS Evolved upgrade precautions apply - verify hardware compatibility, backup configuration, and ensure valid support contract for software updates

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Junos Os Evolved Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-21902 in production — separate from our analysis above.

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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