---
id: CVE-2026-8946
title: 'Incorrect boundary conditions in the Audio/Video: Web Codecs component'
summary: >-
  Incorrect boundary conditions in the Audio/Video: Web Codecs component. This
  vulnerability was fixed in Firefox 151, Firefox ESR 115.36, Firefox ESR
  140.11, Thunderbird 151, and Thunderbird 140.11.
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-119
  - CWE-787
vendor: mozilla
product: firefox
affected:
  - firefox < 115.36.0
  - firefox < 151.0.0
  - 'firefox >= 140.0, < 140.11.0'
  - thunderbird < 140.11
patched:
  - firefox 140.11.0
  - thunderbird 140.11
published: '2026-05-19'
updated: '2026-07-15'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-8946'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2029070'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-46/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-47/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-48/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-50/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-51/'
    label: security@mozilla.org
  - url: 'https://access.redhat.com/errata/RHSA-2026:21378'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:21380'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:21381'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:21382'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:22325'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:22643'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26174'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26268'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26269'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26270'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26491'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26492'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26493'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26521'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26536'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26539'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26551'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26606'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26629'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26630'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:27715'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/security/cve/CVE-2026-8946'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2479849'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-8946.json
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
tags:
  - nvd
epss: 0.0056
epssPercentile: 0.4542
ingestedAt: '2026-07-16T02:48:54.945Z'
---

## Overview

Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

## Affected

- `firefox < 115.36.0`
- `firefox < 151.0.0`
- `firefox >= 140.0, < 140.11.0`
- `thunderbird < 140.11`

## Remediation

Upgrade past the affected range:

- `firefox 140.11.0`
- `thunderbird 140.11`