---
id: CVE-2026-109733
title: 'JIT miscompilation in the JavaScript Engine: JIT component'
summary: >-
  JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability
  was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird
  158, and Thunderbird 153.5.
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N'
cwe:
  - CWE-843
vendor: Mozilla
product: Firefox
affected:
  - Firefox
  - Thunderbird
published: '2026-10-13'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T20:17:07.767'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109733'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2076269'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-106/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-107/'
    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
  - cve.org
epss: 0.00462
epssPercentile: 0.39912
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-15T19:23:24.897351Z'
ingestedAt: '2026-10-13T13:27:04.000Z'
---

## Overview

JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

## Remediation

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