---
id: CVE-2026-71920
title: >-
  Multiple DrayTek VigorSwitch models contain a null pointer dereference
  vulnerability in the formlogout function
summary: >-
  Multiple DrayTek VigorSwitch models contain a null pointer dereference
  vulnerability in the formlogout function. The vulnerability is caused by
  missing checks for an empty or absent Cookie header before string handling. A
  remote attacker…
severity: medium
cvss: 4.9
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-476
published: '2026-08-24'
updated: '2026-10-13'
sourceUpdated: '2026-10-13T09:10:00.323'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-71920'
references:
  - url: >-
      https://www.draytek.com/about/security-advisory/multiple-vulnerabilities-in-vigorswitch-series-august-2026/
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/draytek-vigorswitch-multiple-models-null-pointer-dereference-via-formlogout
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.00556
epssPercentile: 0.44802
ingestedAt: '2026-10-13T09:20:23.182Z'
---

## Overview

Multiple DrayTek VigorSwitch models contain a null pointer dereference vulnerability in the formlogout function. The vulnerability is caused by missing checks for an empty or absent Cookie header before string handling. A remote attacker can trigger this vulnerability via a crafted request to crash the service and cause a denial of service. Exploitation requires valid administrative credentials for the device's web management interface.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.