Juniper Networks PTX Routers Exposed to Critical Security Flaw
Critical Vulnerability Discovered in Juniper Networks’ PTX Series Routers
A critical vulnerability has been discovered in Juniper Networks’ PTX series high-performance routers, which run on the Junos OS Evolved network operating system. The flaw, identified as CVE-2026-21902, affects the On-Box Anomaly detection framework and can be exploited by an unauthenticated attacker with network access to execute arbitrary code with root privileges.
Vulnerability Details
According to Juniper, the vulnerability arises from the fact that the On-Box Anomaly detection framework is reachable over an externally exposed port, despite being intended for internal use only. This allows a remote attacker to access and manipulate the service, potentially gaining complete control of the device. The issue is particularly concerning because the service is enabled by default, requiring no specific configuration.
“If an attacker gains control of a PTX, the impact is bigger than a single device compromise because it can become a traffic vantage point and a control point at the same time,” Sharma explained. “This opens the door to the stealthy interception of data flows, controller redirected traffic, or easy pivots into adjacent networks.”
Impact and Mitigation
The vulnerability has been patched in versions 25.4R1-S1-EVO and 25.4R2-EVO of Junos OS Evolved. Earlier versions, including those prior to 25.4R1-EVO, as well as Junos OS, are not affected.
Piyush Sharma, co-founder and CEO of Tuskira, noted that the vulnerability poses significant risks due to the critical nature of PTX routers in network infrastructure.
“Juniper vulnerabilities have attracted a lot of attention from hackers over the years, due largely in part to the premium positioning they provide if long-term footholds are established,” he said.
Juniper reported that the vulnerability was discovered internally, and t
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