---
id: CVE-2026-111711
title: Netcore NR256CN through 1.5.140116 Pre-Auth Stack Overflow via Boa user_ok()
summary: >-
  Netcore NR256CN through 1.5.140116 contains a pre-authentication stack
  overflow vulnerability in the Boa web server's user_ok() function, which
  copies Basic-auth usernames with unbounded strcpy() calls into 64-byte stack
  buffers. Unauthe…
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-121
vendor: Netcore
product: NR256CN
affected:
  - NR256CN <= 1.5.140116
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-16T20:53:29.394899Z'
published: '2026-10-16'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T21:16:42.070Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-111711'
references:
  - url: >-
      https://github.com/lukadqq/netcore-router-public-refs/blob/a44d562736b41c944223297e9144d2ad7fa2aff1/2026.10.15-netcore-nr256cn-basic-auth-stack-overflow.md
  - url: >-
      https://www.vulncheck.com/advisories/netcore-nr256cn-through-1.5.140116-pre-auth-stack-overflow-via-boa-user-ok
    label: >-
      VulnCheck Advisory: Netcore NR256CN through 1.5.140116 Pre-Auth Stack
      Overflow via Boa user_ok()
tags:
  - cve.org
ingestedAt: '2026-10-16T18:43:08.639Z'
---

## Overview

Netcore NR256CN through 1.5.140116 contains a pre-authentication stack overflow vulnerability in the Boa web server's user_ok() function, which copies Basic-auth usernames with unbounded strcpy() calls into 64-byte stack buffers. Unauthenticated attackers can send a username longer than 63 bytes to any protected /router/*.cgi route to crash the main Boa process or potentially execute code.

## Affected

- `NR256CN <= 1.5.140116`

## Remediation

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