---
id: CVE-2026-86871
title: An integer underflow was addressed with improved input validation
summary: >-
  An integer underflow was addressed with improved input validation. This issue
  is fixed in macOS Golden Gate 27, macOS Sequoia 15.8, macOS Tahoe 26.7. An
  attacker with control of a network file server may be able to cause unexpected
  syste…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: adp
vendor: Apple
product: macOS
affected:
  - macOS < 15.8
  - macOS < 26.7
  - macOS < 27
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-20T14:39:26.599060Z'
published: '2026-10-20'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T20:39:46.185Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-86871'
references:
  - url: 'https://support.apple.com/en-us/149035'
  - url: 'https://support.apple.com/en-us/149042'
  - url: 'https://support.apple.com/en-us/149043'
tags:
  - cve.org
epss: 0.00489
epssPercentile: 0.41857
ingestedAt: '2026-10-20T01:49:42.598Z'
---

## Overview

An integer underflow was addressed with improved input validation. This issue is fixed in macOS Golden Gate 27, macOS Sequoia 15.8, macOS Tahoe 26.7. An attacker with control of a network file server may be able to cause unexpected system termination.

## Affected

- `macOS < 15.8`
- `macOS < 26.7`
- `macOS < 27`

## Remediation

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