---
id: CVE-2025-0240
title: >-
  Parsing a JavaScript module as JSON could, under some circumstances, cause
  cross-compartment access, which may result in a use-after-free
summary: >-
  Parsing a JavaScript module as JSON could, under some circumstances, cause
  cross-compartment access, which may result in a use-after-free. This
  vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134,
  and Thunderbird 1…
severity: medium
cvss: 4
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'
cwe:
  - CWE-416
vendor: mozilla
product: firefox
affected:
  - firefox < 128.6.0
  - firefox < 134.0
  - thunderbird < 128.6.0
  - 'thunderbird >= 129.0, < 134.0'
patched:
  - firefox 134.0
  - thunderbird 134.0
published: '2025-01-07'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T19:10:01.007'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-0240'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=1929623'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-01/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-02/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-04/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-05/'
    label: security@mozilla.org
  - url: 'https://lists.debian.org/debian-lts-announce/2025/01/msg00004.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00672
epssPercentile: 0.50188
ingestedAt: '2026-09-30T19:21:07.218Z'
---

## Overview

Parsing a JavaScript module as JSON could, under some circumstances, cause cross-compartment access, which may result in a use-after-free. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

## Affected

- `firefox < 128.6.0`
- `firefox < 134.0`
- `thunderbird < 128.6.0`
- `thunderbird >= 129.0, < 134.0`

## Remediation

Upgrade past the affected range:

- `firefox 134.0`
- `thunderbird 134.0`