---
id: CVE-2026-88831
title: >-
  BusyBox httpd IP deny rules with invalid CIDR prefix lengths fail open,
  leaving a parsed IP with a zeroed mask so the rule matches no clients.
summary: >-
  BusyBox httpd IP deny rules with invalid CIDR prefix lengths fail open,
  leaving a parsed IP with a zeroed mask so the rule matches no clients.
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'
cwe:
  - CWE-636
vendor: Red Hat
product: busybox-main
affected:
  - busybox-main (all versions)
published: '2026-09-23'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T23:16:54.457'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-88831'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2026:72111'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2026-88831'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2531346'
    label: secalert@redhat.com
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-88831.json
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-88831'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-88831'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-23T18:08:33.797869Z'
epss: 0.00205
epssPercentile: 0.09325
ingestedAt: '2026-09-23T18:29:33.145Z'
patched:
  - hardened_images
---

## Overview

BusyBox httpd IP deny rules with invalid CIDR prefix lengths fail open, leaving a parsed IP with a zeroed mask so the rule matches no clients.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Hardened Images · no fix planned: Red Hat Hardened Images · updated 2026-09-24 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-88831.json)
- **RHSA-2026:72111** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-25 · [advisory](https://access.redhat.com/errata/RHSA-2026:72111)