---
id: CVE-2026-100818
title: 'Sandbox escape due to use-after-free in the Widget: Gtk component'
summary: >-
  Sandbox escape due to use-after-free in the Widget: Gtk component. This
  vulnerability was fixed in Firefox ESR 153.4, Firefox 157, and Firefox ESR
  140.17.
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
vendor: Mozilla
product: Firefox
affected:
  - Firefox
published: '2026-09-29'
updated: '2026-09-29'
sourceUpdated: '2026-09-29T14:17:17.550'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100818'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2069399'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-100/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-97/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-99/'
    label: security@mozilla.org
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-29T13:13:15.417892Z'
ingestedAt: '2026-09-29T13:34:31.675Z'
---

## Overview

Sandbox escape due to use-after-free in the Widget: Gtk component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17.

## Remediation

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