---
id: CVE-2025-8040
title: >-
  Memory safety bugs present in Firefox ESR 140.0, Thunderbird ESR 140.0,
  Firefox 140 and Thunderbird 140
summary: >-
  Memory safety bugs present in Firefox ESR 140.0, Thunderbird ESR 140.0,
  Firefox 140 and Thunderbird 140. Some of these bugs showed evidence of memory
  corruption and we presume that with enough effort some of these could have
  been exploit…
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-119
vendor: mozilla
product: firefox
affected:
  - firefox < 140.1
  - firefox < 141.0
  - thunderbird < 140.1
  - thunderbird < 141.0
patched:
  - firefox 141.0
  - thunderbird 141.0
published: '2025-07-22'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T18:10:00.190'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-8040'
references:
  - url: 'https://bugzilla.mozilla.org/buglist.cgi?bug_id=1975058%2C1975998'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-56/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-59/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-61/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-63/'
    label: security@mozilla.org
tags:
  - nvd
epss: 0.00323
epssPercentile: 0.22957
ingestedAt: '2026-09-30T18:17:24.451Z'
---

## Overview

Memory safety bugs present in Firefox ESR 140.0, Thunderbird ESR 140.0, Firefox 140 and Thunderbird 140. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 141, Firefox ESR 140.1, Thunderbird 141, and Thunderbird 140.1.

## Affected

- `firefox < 140.1`
- `firefox < 141.0`
- `thunderbird < 140.1`
- `thunderbird < 141.0`

## Remediation

Upgrade past the affected range:

- `firefox 141.0`
- `thunderbird 141.0`