---
id: CVE-2025-5272
title: Memory safety bugs present in Firefox 138 and Thunderbird 138
summary: >-
  Memory safety bugs present in Firefox 138 and Thunderbird 138. 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
  vulnerabili…
severity: high
cvss: 7.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L'
cwe:
  - CWE-787
vendor: mozilla
product: firefox
affected:
  - firefox < 139.0
  - thunderbird < 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-2025-5272'
references:
  - url: >-
      https://bugzilla.mozilla.org/buglist.cgi?bug_id=1726254%2C1742738%2C1960121
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-42/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-45/'
    label: security@mozilla.org
tags:
  - nvd
epss: 0.00326
epssPercentile: 0.23251
ingestedAt: '2026-09-30T18:17:24.441Z'
---

## Overview

Memory safety bugs present in Firefox 138 and Thunderbird 138. 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 and Thunderbird 139.

## Affected

- `firefox < 139.0`
- `thunderbird < 139.0`

## Remediation

Upgrade past the affected range:

- `firefox 139.0`
- `thunderbird 139.0`