---
id: CVE-2025-5270
title: >-
  In certain cases, SNI could have been sent unencrypted even when encrypted DNS
  was enabled
summary: >-
  In certain cases, SNI could have been sent unencrypted even when encrypted DNS
  was enabled. This vulnerability was fixed in Firefox 139 and Thunderbird 139.
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-319
vendor: mozilla
product: firefox
affected:
  - firefox < 139.0
patched:
  - firefox 139.0
published: '2025-05-27'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T18:10:00.190'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-5270'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=1910298'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-42/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-45/'
    label: security@mozilla.org
tags:
  - nvd
epss: 0.00286
epssPercentile: 0.1902
ingestedAt: '2026-09-30T18:17:24.440Z'
---

## Overview

In certain cases, SNI could have been sent unencrypted even when encrypted DNS was enabled. This vulnerability was fixed in Firefox 139 and Thunderbird 139.

## Affected

- `firefox < 139.0`

## Remediation

Upgrade past the affected range:

- `firefox 139.0`