---
id: CVE-2025-8037
title: >-
  Setting a nameless cookie with an equals sign in the value shadowed other
  cookies
summary: >-
  Setting a nameless cookie with an equals sign in the value shadowed other
  cookies. Even if the nameless cookie was set over HTTP and the shadowed cookie
  included the `Secure` attribute. This vulnerability was fixed in Firefox 141,
  Firefo…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-614
vendor: mozilla
product: firefox
affected:
  - firefox < 140.1
  - firefox < 141.0
  - thunderbird < 140.1
  - thunderbird < 141.0
patched:
  - firefox 141.0
  - thunderbird 141.0
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-2025-8037'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=1964767'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-56/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-59/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-61/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-63/'
    label: security@mozilla.org
tags:
  - nvd
epss: 0.00234
epssPercentile: 0.12904
ingestedAt: '2026-09-30T18:17:24.450Z'
---

## Overview

Setting a nameless cookie with an equals sign in the value shadowed other cookies. Even if the nameless cookie was set over HTTP and the shadowed cookie included the `Secure` attribute. This vulnerability was fixed in Firefox 141, Firefox ESR 140.1, Thunderbird 141, and Thunderbird 140.1.

## Affected

- `firefox < 140.1`
- `firefox < 141.0`
- `thunderbird < 140.1`
- `thunderbird < 141.0`

## Remediation

Upgrade past the affected range:

- `firefox 141.0`
- `thunderbird 141.0`