---
id: CVE-2026-100804
title: 'Sandbox escape due to use-after-free in the Preferences: Backend component'
summary: >-
  Sandbox escape due to use-after-free in the Preferences: Backend component.
  This vulnerability was fixed in Thunderbird 157 and Firefox 157.
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
vendor: Mozilla
product: Firefox
affected:
  - Firefox
published: '2026-09-29'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T18:18:09.633'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100804'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2058647'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-101/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-97/'
    label: security@mozilla.org
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-100804.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-100804'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2543173'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-100804'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100804'
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-97/#CVE-2026-100804'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00282
epssPercentile: 0.20634
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-29T14:28:13.785043Z'
ingestedAt: '2026-09-29T13:34:31.670Z'
scores:
  nvd: 9.6
  vendor: 6.1
---

## Overview

Sandbox escape due to use-after-free in the Preferences: Backend component. This vulnerability was fixed in Thunderbird 157 and Firefox 157.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Moderate · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-100804.json)