---
id: CVE-2026-109750
title: 'Site isolation issue in the DOM: Web Authentication component'
summary: >-
  Site isolation issue in the DOM: Web Authentication component. This
  vulnerability was fixed in Firefox 158 and Thunderbird 158.
severity: critical
published: '2026-10-13'
updated: '2026-10-13'
sourceUpdated: '2026-10-13T19:18:39.180'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109750'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2067571'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-106/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-109/'
    label: security@mozilla.org
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-13T13:27:04.007Z'
vendor: Mozilla
product: Firefox
affected:
  - Firefox
  - Thunderbird
epss: 0.0038
epssPercentile: 0.31813
cvss: 9.6
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H'
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-19T20:37:17.777350Z'
cvssSource: adp
---

## Overview

Site isolation issue in the DOM: Web Authentication component. This vulnerability was fixed in Firefox 158 and Thunderbird 158.

## Remediation

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