---
id: "CVE-2026-103411"
kind: "vulnerability"
aliases: ["CVE-2026-103411"]
title: "Juniper Session Smart Router: DHCP decoder underflow leaks data, crashes service"
severity: "high"
cvss: 7.1
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["adjacent-network", "infrastructure", "juniper", "network-appliance", "session-smart-router"]
not_affected_if: []
published_at: "2026-10-28T17:17:28+00:00"
first_seen_at: "2026-10-28T17:34:08+00:00"
updated_at: "2026-10-28T17:35:15+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-103411", "first_seen_at": "2026-10-28T17:34:08+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-10-28T17:35:15+00:00"}]
---

# Juniper Session Smart Router: DHCP decoder underflow leaks data, crashes service

An integer underflow in the DHCP message decoder of Juniper Session Smart Router lets a device on the local network send a malicious DHCP reply. The attacker can read information from the router and cause a denial of service.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-28T17:34:08+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-103411
- 2026-10-28T17:35:15+00:00 analyst — Juniper's advisory for this CVE is not retrievable yet (CVE published minutes ago; supportportal pages render JS-only, NVD fetch returned nothing). Affected/fixed versions and whether DHCP client mode is required stay unknown; nothing verified. An unconfirmed lead: CERT-FR CERTFR-2026-AVI-1337 cites Juniper JSA112528 (2026-10-16 SSR patch release notice, SSR <7.0.5, 7.1.x <7.1.7, 7.2.x <7.2.3), but it does not name this CVE, so I did not record it as a fix. Revisit when the Juniper JSA appears. NVD gives CVSS 3.1 7.1 AV:A/PR:N, low confidentiality impact, high availability impact, so the attacker has to be on the same L2 segment as the router.

## From the sources

An Integer Underflow vulnerability in DhcpMessageDecoder in Juniper Networks Session Smart Router allows an attacker with local network access to cause information disclosure and a denial of service via a malicious DHCP reply.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_