---
id: CVE-2026-109705
title: >-
  Sandbox escape, site isolation issue due to incorrect boundary conditions,
  use-after-free in the Networking component
summary: >-
  Sandbox escape, site isolation issue due to incorrect boundary conditions,
  use-after-free in the Networking component. This vulnerability was fixed in
  Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
severity: critical
cvss: 9.6
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H'
cwe:
  - CWE-416
  - CWE-825
published: '2026-10-13'
updated: '2026-10-13'
sourceUpdated: '2026-10-13T19:18:33.667'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109705'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2040905'
    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
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-109705.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-109705'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2550413'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-109705'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109705'
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-108/#CVE-2026-109705'
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-110/#CVE-2026-109705'
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-119/'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
ingestedAt: '2026-10-13T13:27:03.990Z'
vendor: Mozilla
product: Firefox
affected:
  - Firefox
  - Thunderbird
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-13T14:14:35.331154Z'
epss: 0.00311
epssPercentile: 0.23838
scores:
  nvd: 9.6
  vendor: 7.5
  adp: 9.6
---

## Overview

Sandbox escape, site isolation issue due to incorrect boundary conditions, use-after-free 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.

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, … · updated 2026-10-22 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-109705.json)