---
id: CVE-2026-102761
title: >-
  NetX Duo's WebSocket client resets the unmasking cursor to the first
  `NX_PACKET` each time it advances through a chained packet, while the loop's
  upper bound belongs to the current packet
summary: >-
  NetX Duo's WebSocket client resets the unmasking cursor to the first
  `NX_PACKET` each time it advances through a chained packet, while the loop's
  upper bound belongs to the current packet. With the standard contiguous
  packet-pool layout,…
severity: critical
cvss: 9.3
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'
cwe:
  - CWE-787
vendor: Eclipse Foundation
product: NetX Duo
affected:
  - netx_duo >= 6.2.0 <= 6.5.1.202602
published: '2026-09-29'
updated: '2026-09-29'
sourceUpdated: '2026-09-29T18:17:13.450'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102761'
references:
  - url: >-
      https://github.com/eclipse-threadx/netxduo/security/advisories/GHSA-6xgx-v7gw-qjph
    label: emo@eclipse.org
tags:
  - nvd
  - cve.org
cvssSource: cna
ingestedAt: '2026-09-29T17:41:02.254Z'
---

## Overview

NetX Duo's WebSocket client resets the unmasking cursor to the first `NX_PACKET` each time it advances through a chained packet, while the loop's upper bound belongs to the current packet. With the standard contiguous packet-pool layout, a masked server frame split across two packets therefore drives the XOR loop through the first packet's unused payload area and on through the second packet's `NX_PACKET` control block.



The four-byte WebSocket masking key controls the bytes written, so the corruption is attacker-chosen rather than incidental.

## Remediation

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