---
id: CVE-2025-4093
title: 'Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9'
summary: >-
  Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This
  bug showed evidence of memory corruption and we presume that with enough
  effort this could have been exploited to run arbitrary code. This
  vulnerability was fixe…
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 < 128.10
  - thunderbird < 128.10.0
patched:
  - firefox 128.10
  - thunderbird 128.10.0
published: '2025-04-29'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T18:10:00.190'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-4093'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=1894100'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-29/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-32/'
    label: security@mozilla.org
  - url: 'https://lists.debian.org/debian-lts-announce/2025/05/msg00024.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00483
epssPercentile: 0.3929
ingestedAt: '2026-09-30T18:17:24.437Z'
---

## Overview

Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.10 and Thunderbird 128.10.

## Affected

- `firefox < 128.10`
- `thunderbird < 128.10.0`

## Remediation

Upgrade past the affected range:

- `firefox 128.10`
- `thunderbird 128.10.0`