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CriticalVulnerabilityCVE-2026-103409updated 28 Oct 2026, 20:42 UTC

Juniper Session Smart Router: unauthenticated admin takeover over the network

Someone on the network can send specially crafted web requests to a router that has not yet been set up in Juniper's cloud management, and gain full administrator control without logging in. Once the router is connected to Mist/Conductor, t

Official, 2 sources
SeverityCriticalCVSS 9.8 of 10
Being exploited?UnclearNo reports either way yet
Fix available?UnclearNo fixed version published in the sources yet
How sure is this?Official, 2 sourcesBacked by an official source

How the attack works simplified

  1. 1Attacker on networkSends crafted URL parameters
  2. 2Insecure endpointAccepts request without authentication
  3. 3Root executionEndpoint runs as root
  4. 4Admin privilegesAttacker gains administrator access
  5. ResultAttacker controls the router as admin

What happened

A missing-authentication flaw in a critical function of Juniper Networks Session Smart Router lets an unauthenticated network attacker pass crafted URL parameters to an insecure endpoint that runs as root, gaining administrative privileges.

Why it is dangerous: An attacker who reaches the device over the network can take complete control of it as root, which could expose or redirect traffic passing through the router. Devices not yet onboarded to Mist/Conductor are exposed during setup.

Are you affected?

You are affected if you run Juniper Session Smart Router devices that have not yet been onboarded to Mist/Conductor and are reachable from a network where an attacker could send requests.

Juniper Networks Session Smart Router, devices prior to onboarding to Mist/Conductor (exact versions unknown from the material)

What to do

  1. Onboard the Session Smart Router to Mist/Conductor as soon as possible, since the flaw cannot be exploited after onboarding
  2. Restrict network access to the router's management interfaces so untrusted hosts cannot reach them
  3. Check Juniper's official advisory for a fixed software version and apply it

Timeline

  1. 28 Oct 2026, 17:17 UTC
    Publicly disclosed
  2. 28 Oct 2026, 17:17 UTC
    Reported by NVD · NVD
  3. 28 Oct 2026, 17:22 UTC
    Picked up by Zero Radar
  4. 28 Oct 2026, 20:42 UTC
    GitHub Advisory reported on it · GitHub Advisory

Sources 2 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-103409 · GHSA-4j2g-4264-38mr
CVSS
9.8 / 10
EPSS
0.3% chance of exploitation within 30 days
Disclosed
28 Oct 2026, 17:17 UTC
On Zero Radar
28 Oct 2026, 17:22 UTC (5 min after disclosure)
Last change
28 Oct 2026, 20:42 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

Juniper Session Smart Router: unauthenticated admin takeover over the network · Zero Radar