---
id: CVE-2025-1017
title: >-
  Memory safety bugs present in Firefox 134, Thunderbird 134, Firefox ESR 128.6,
  and Thunderbird 128.6
summary: >-
  Memory safety bugs present in Firefox 134, Thunderbird 134, Firefox ESR 128.6,
  and Thunderbird 128.6. Some of these bugs showed evidence of memory corruption
  and we presume that with enough effort some of these could have been exploited
  …
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-787
  - CWE-787
vendor: mozilla
product: firefox
affected:
  - firefox < 128.7.0
  - firefox < 135.0
  - 'thunderbird >= 128.0.1, < 128.7.0'
  - 'thunderbird >= 131.0, < 135.0'
patched:
  - firefox 135.0
  - thunderbird 135.0
published: '2025-02-04'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T19:10:01.007'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-1017'
references:
  - url: >-
      https://bugzilla.mozilla.org/buglist.cgi?bug_id=1926256%2C1935984%2C1935471
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-07/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-09/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-10/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-11/'
    label: security@mozilla.org
  - url: 'https://lists.debian.org/debian-lts-announce/2025/02/msg00006.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00579
epssPercentile: 0.45546
ingestedAt: '2026-09-30T19:21:07.224Z'
---

## Overview

Memory safety bugs present in Firefox 134, Thunderbird 134, Firefox ESR 128.6, and Thunderbird 128.6. 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 135, Firefox ESR 128.7, Thunderbird 128.7, and Thunderbird 135.

## Affected

- `firefox < 128.7.0`
- `firefox < 135.0`
- `thunderbird >= 128.0.1, < 128.7.0`
- `thunderbird >= 131.0, < 135.0`

## Remediation

Upgrade past the affected range:

- `firefox 135.0`
- `thunderbird 135.0`