Juniper PTX Routers at Risk, Critical Takeover Flaw Disclosed

Juniper Tells Customers to Tune Their Firewall Greg Sirico • March 3, 2026

A critical vulnerability in Juniper Networks' primary operating system could give threat actors root level privileges to execute code on Juniper’s PTX Series routers.

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Tracked as CVE-2026-21902 with a CVSS score of 9.3, the flaw derives from an improper permission assignment in Junos OS Evolved - specifically in the On-Box Anomaly Detection framework that handles internal monitoring and should be accessible only from an internal routing interface.

Researchers at watchTowr notified the company of the flaw. Juniper in a Tuesday advisory told customers to filter access through access lists or firewalls and that it will later develop a patch.

Since the service runs as root and enabled by default, successful exploitation would give attackers full command and control over devices without the need for ...