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VulnerabilityPublished Updated

CVE-2026-21902: Juniper Networks Junos OS Evolved · Incorrect Permissions

Affects Juniper Networks Junos OS EvolvedSource CVE Database V5

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Not known to be exploited · 18% EPSS · CVSS 9.8 Critical : upgrade to 25.4R1-S1-EVO as a priority.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
18.4% chance of exploitation in 30 days – higher than 97% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 25.4R1-S1-EVO
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 25 Feb 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    Public exploit code: GitHub proofs of concept

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), GitHub proofs of concept, the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade Juniper Networks Junos OS Evolved to 25.4R1-S1-EVO.

Affected software

ProductAffectedFixed in
Juniper NetworksJunos OS EvolvedAffected
  • =25.4
Fixed in
  • 25.4R1-S1-EVO

AI-suggested

To mitigate CVE-2026-21902, organizations should immediately upgrade affected Junos OS Evolved PTX Series devices to versions 25.4R1-S1-EVO, 25.4R2-EVO, or later where the vulnerability is patched. If you cannot patch yet, network administrators should restrict access to the On-Box Anomaly detection framework by implementing strict firewall rules or access control lists (ACLs) that block external access to the service ports. Verify and enforce that the anomaly detection framework is only reachable via the internal routing instance as intended. Disable the On-Box Anomaly detection framework if it is not essential for operational needs. Regularly audit device configurations to ensure no unintended exposure of internal services. Monitor network traffic and device logs for suspicious activity indicative of exploitation attempts. Additionally, consider segmenting management and control plane traffic from general network traffic to reduce exposure. Engage with Juniper Networks support for guidance and to confirm remediation status. Maintain an incident response plan tailored to network infrastructure compromise scenarios.

Description

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.

References

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