---
id: CVE-2026-120596
title: CVE-2026-120596
summary: >-
  A remotely exploitable denial-of-service vulnerability exists in the TCP
  options parser of the Nut/Net TCP/IP stack included in Nut/OS, developed by
  Ethernut/Egnite. Nut/OS releases up to version 5.1 are affected. An
  unauthenticated atta…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: adp
cwe:
  - CWE-835
  - CWE-119
  - CWE-20
vendor: Ethernut / egnite GmbH
product: Nut/Net TCP/IP Stack
affected:
  - nut_net_tcp_ip_stack Nut/OS 5.1
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-11-02T17:17:32.319063Z'
published: '2026-11-02'
updated: '2026-11-02'
sourceUpdated: '2026-11-02T17:17:35.066Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-120596'
references:
  - url: 'https://www.ethernut.de/en/download/index.html'
tags:
  - cve.org
epss: 0.00375
epssPercentile: 0.31726
ingestedAt: '2026-11-05T19:30:42.724Z'
---

## Overview

A remotely exploitable denial-of-service vulnerability exists in the TCP options parser of the Nut/Net TCP/IP stack included in Nut/OS, developed by Ethernut/Egnite. Nut/OS releases up to version 5.1 are affected. An unauthenticated attacker can send a single TCP segment containing an unknown TCP option with a length byte of zero to any open TCP port on a vulnerable device. When processed, this malformed option triggers an infinite loop in the function NutTcpInputOptions, permanently blocking the TCP processing thread and rendering all TCP-based services unresponsive until the device is rebooted.

## Affected

- `nut_net_tcp_ip_stack Nut/OS 5.1`

## Remediation

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