---
id: CVE-2025-8027
title: >-
  On 64-bit platforms IonMonkey-JIT only wrote 32 bits of the 64-bit return
  value space on the stack
summary: >-
  On 64-bit platforms IonMonkey-JIT only wrote 32 bits of the 64-bit return
  value space on the stack. Baseline-JIT, however, read the entire 64 bits. This
  vulnerability was fixed in Firefox 141, Firefox ESR 115.26, Firefox ESR
  128.13, Fire…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N'
cwe:
  - CWE-457
vendor: mozilla
product: firefox
affected:
  - firefox < 115.26.0
  - firefox < 141.0
  - 'firefox >= 128.0, < 128.13.0'
  - 'firefox >= 140.0, < 140.1.0'
  - thunderbird < 128.13.0
  - thunderbird < 141.0
  - 'thunderbird >= 140.0, < 140.1.0'
patched:
  - firefox 140.1.0
  - thunderbird 140.1.0
published: '2025-07-22'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T18:10:00.190'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-8027'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=1968423'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-56/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-57/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-58/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-59/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-61/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-62/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-63/'
    label: security@mozilla.org
  - url: 'https://lists.debian.org/debian-lts-announce/2025/07/msg00016.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00379
epssPercentile: 0.29387
ingestedAt: '2026-09-30T18:17:24.446Z'
---

## Overview

On 64-bit platforms IonMonkey-JIT only wrote 32 bits of the 64-bit return value space on the stack. Baseline-JIT, however, read the entire 64 bits. This vulnerability was fixed in Firefox 141, Firefox ESR 115.26, Firefox ESR 128.13, Firefox ESR 140.1, Thunderbird 141, Thunderbird 128.13, and Thunderbird 140.1.

## Affected

- `firefox < 115.26.0`
- `firefox < 141.0`
- `firefox >= 128.0, < 128.13.0`
- `firefox >= 140.0, < 140.1.0`
- `thunderbird < 128.13.0`
- `thunderbird < 141.0`
- `thunderbird >= 140.0, < 140.1.0`

## Remediation

Upgrade past the affected range:

- `firefox 140.1.0`
- `thunderbird 140.1.0`