---
id: CVE-2025-5268
title: >-
  Memory safety bugs present in Firefox 138, Thunderbird 138, Firefox ESR
  128.10, and Thunderbird 128.10
summary: >-
  Memory safety bugs present in Firefox 138, Thunderbird 138, Firefox ESR
  128.10, and Thunderbird 128.10. Some of these bugs showed evidence of memory
  corruption and we presume that with enough effort some of these could have
  been exploite…
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-119
vendor: mozilla
product: firefox
affected:
  - firefox < 128.11.0
  - firefox < 139.0
  - thunderbird < 128.11.0
  - 'thunderbird >= 129.0, < 139.0'
patched:
  - firefox 139.0
  - thunderbird 139.0
published: '2025-05-27'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T18:10:00.190'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-5268'
references:
  - url: >-
      https://bugzilla.mozilla.org/buglist.cgi?bug_id=1950136%2C1958121%2C1960499%2C1962634
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-42/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-44/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-45/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-46/'
    label: security@mozilla.org
  - url: 'https://lists.debian.org/debian-lts-announce/2025/05/msg00043.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2025/05/msg00046.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00489
epssPercentile: 0.39736
ingestedAt: '2026-09-30T18:17:24.440Z'
---

## Overview

Memory safety bugs present in Firefox 138, Thunderbird 138, Firefox ESR 128.10, and Thunderbird 128.10. 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 139, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.

## Affected

- `firefox < 128.11.0`
- `firefox < 139.0`
- `thunderbird < 128.11.0`
- `thunderbird >= 129.0, < 139.0`

## Remediation

Upgrade past the affected range:

- `firefox 139.0`
- `thunderbird 139.0`