---
id: CVE-2025-2817
title: >-
  Thunderbird's update mechanism allowed a medium-integrity user process to
  interfere with the SYSTEM-level updater by manipulating the file-locking
  behavior
summary: >-
  Thunderbird's update mechanism allowed a medium-integrity user process to
  interfere with the SYSTEM-level updater by manipulating the file-locking
  behavior. By injecting code into the user-privileged process, an attacker
  could bypass int…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-22
vendor: mozilla
product: firefox
affected:
  - firefox < 115.23.0
  - firefox < 138.0
  - 'firefox >= 116.0, < 128.10.0'
  - thunderbird < 128.10.0
  - 'thunderbird >= 129.0, < 138.0'
patched:
  - firefox 128.10.0
  - thunderbird 138.0
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-2025-2817'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=1917536'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-28/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-29/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-30/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-31/'
    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/msg00022.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00656
epssPercentile: 0.495
ingestedAt: '2026-09-30T18:17:24.432Z'
---

## Overview

Thunderbird's update mechanism allowed a medium-integrity user process to interfere with the SYSTEM-level updater by manipulating the file-locking behavior. By injecting code into the user-privileged process, an attacker could bypass intended access controls, allowing SYSTEM-level file operations on paths controlled by a non-privileged user and enabling privilege escalation. This vulnerability was fixed in Firefox 138, Firefox ESR 128.10, Firefox ESR 115.23, Thunderbird 138, and Thunderbird 128.10.

## Affected

- `firefox < 115.23.0`
- `firefox < 138.0`
- `firefox >= 116.0, < 128.10.0`
- `thunderbird < 128.10.0`
- `thunderbird >= 129.0, < 138.0`

## Remediation

Upgrade past the affected range:

- `firefox 128.10.0`
- `thunderbird 138.0`