---
id: CVE-2026-109759
title: Site isolation issue in the Networking component
summary: >-
  Site isolation issue in the Networking component. This vulnerability was fixed
  in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
severity: none
published: '2026-10-13'
updated: '2026-10-13'
sourceUpdated: '2026-10-13T19:18:40.063'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109759'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2070252'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-106/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-108/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-109/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-110/'
    label: security@mozilla.org
tags:
  - nvd
ingestedAt: '2026-10-13T13:27:04.010Z'
---

## Overview

Site isolation issue in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

## Remediation

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