---
id: CVE-2026-92040
title: 'Use-after-free in the JavaScript: WebAssembly component'
summary: >-
  Use-after-free in the JavaScript: WebAssembly component. This vulnerability
  was fixed in Firefox 156 and Thunderbird 156.
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'
cwe:
  - CWE-416
  - CWE-825
vendor: mozilla
product: firefox
affected:
  - firefox < 156.0.0
  - thunderbird < 156.0
patched:
  - firefox 156.0.0
  - thunderbird 156.0
published: '2026-09-15'
updated: '2026-10-05'
sourceUpdated: '2026-10-05T17:52:59.387'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-92040'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2024248'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-90/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-94/'
    label: security@mozilla.org
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-92040.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-92040'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2533763'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-92040'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-92040'
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-90/#CVE-2026-92040'
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-94/#CVE-2026-92040'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00422
epssPercentile: 0.3635
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-20T00:19:32.366879Z'
scores:
  nvd: 8.8
  vendor: 6.1
  adp: 8.8
ingestedAt: '2026-09-15T12:36:50.186Z'
---

## Overview

Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 156 and Thunderbird 156.

## Affected

- `firefox < 156.0.0`
- `thunderbird < 156.0`

## Remediation

Upgrade past the affected range:

- `firefox 156.0.0`
- `thunderbird 156.0`

## Vendor advisories

- **Red Hat VEX** · Moderate · updated 2026-09-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-92040.json)