---
id: CVE-2026-38821
title: >-
  A heap-based buffer overflow vulnerability exists in openNDS before 11.0.0
  that allows an unauthenticated attacker on the captive portal network to crash
  the openNDS daemon (denial of service) and potentially achieve remote code
  executio…
summary: >-
  A heap-based buffer overflow vulnerability exists in openNDS before 11.0.0
  that allows an unauthenticated attacker on the captive portal network to crash
  the openNDS daemon (denial of service) and potentially achieve remote code
  executio…
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L'
cwe:
  - CWE-122
published: '2026-08-28'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T15:54:36.797'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-38821'
references:
  - url: >-
      https://github.com/openNDS/openNDS/commit/3b5f7ef40cd048826d3c4a16f61a73a1768fd5a9
    label: cve@mitre.org
tags:
  - nvd
epss: 0.00307
epssPercentile: 0.20924
ingestedAt: '2026-09-09T16:14:05.517Z'
---

## Overview

A heap-based buffer overflow vulnerability exists in openNDS before 11.0.0 that allows an unauthenticated attacker on the captive portal network to crash the openNDS daemon (denial of service) and potentially achieve remote code execution. This is in http_microhttpd.c.

## Remediation

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