---
id: CVE-2026-5067
title: >-
  Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated
  Sec-WebSocket-Key
summary: >-
  A remote, unauthenticated attacker can trigger memory corruption in Zephyr's
  HTTP server WebSocket upgrade path by sending a crafted Sec-WebSocket-Key
  header. The HTTP/1 header parser copies the header into a fixed-size buffer
  using a bo…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-170
  - CWE-787
vendor: zephyrproject-rtos
product: Zephyr
affected:
  - Zephyr >= 3.7.0 < 4.3.1
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-06-09T13:11:48.752906Z'
exploitAvailable: true
published: '2026-06-09'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T22:10:25.382Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-5067'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-wgr4-9pwq-94vj
tags:
  - cve.org
  - exploit-available
epss: 0.00865
epssPercentile: 0.57756
ingestedAt: '2026-10-15T22:48:25.574Z'
---

## Overview

A remote, unauthenticated attacker can trigger memory corruption in Zephyr's HTTP server WebSocket upgrade path by sending a crafted Sec-WebSocket-Key header. The HTTP/1 header parser copies the header into a fixed-size buffer using a bounded copy that does not guarantee NUL termination when the input length reaches the buffer size. During upgrade handling the buffer is copied to a local stack buffer and passed to strlen(); if no NUL exists in-bounds, strlen() reads beyond the stack buffer and subsequent concatenation with the WebSocket magic string can write out of bounds. This leads to out-of-bounds read and write on stack memory, resulting in crash (denial of service) and potentially code execution. The path is reachable when CONFIG_HTTP_SERVER_WEBSOCKET is enabled.

## Affected

- `Zephyr >= 3.7.0 < 4.3.1`

## Remediation

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