---
id: CVE-2025-1933
title: >-
  On 64-bit CPUs, when the JIT compiles WASM i32 return values they can pick up
  bits from left over memory
summary: >-
  On 64-bit CPUs, when the JIT compiles WASM i32 return values they can pick up
  bits from left over memory. This can potentially cause them to be treated as a
  different type. This vulnerability was fixed in Firefox 136, Firefox ESR
  115.21,…
severity: high
cvss: 7.6
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H'
vendor: mozilla
product: firefox
affected:
  - firefox < 115.21.0
  - firefox < 136.0
  - 'firefox >= 116.0, < 128.8.0'
  - thunderbird < 128.8
  - 'thunderbird >= 129.0, < 136.0'
patched:
  - firefox 128.8.0
  - thunderbird 136.0
published: '2025-03-04'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T19:10:01.007'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-1933'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=1946004'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-14/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-15/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-16/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-17/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-18/'
    label: security@mozilla.org
  - url: 'https://lists.debian.org/debian-lts-announce/2025/03/msg00006.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00319
epssPercentile: 0.22439
ingestedAt: '2026-09-30T19:21:07.227Z'
---

## Overview

On 64-bit CPUs, when the JIT compiles WASM i32 return values they can pick up bits from left over memory. This can potentially cause them to be treated as a different type. This vulnerability was fixed in Firefox 136, Firefox ESR 115.21, Firefox ESR 128.8, Thunderbird 136, and Thunderbird 128.8.

## Affected

- `firefox < 115.21.0`
- `firefox < 136.0`
- `firefox >= 116.0, < 128.8.0`
- `thunderbird < 128.8`
- `thunderbird >= 129.0, < 136.0`

## Remediation

Upgrade past the affected range:

- `firefox 128.8.0`
- `thunderbird 136.0`