CVE-2025-5270

SNI was sometimes unencrypted

7.5 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: High
Integrity: None
Availability: None

Exploit likelihood

0.29%Up 0.3 points since May 28, 2025

What each source reports

CVE List Score used 7.5

SNI was sometimes unencrypted

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.

Record: CVE-2025-5270
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness: CWE-319
Updated: 2026-11-02

EUVDEUVD-2025-18106 7.5

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.

Record: EUVD-2025-18106
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-hf6r-227w-qwf9 7.5

In certain cases, SNI could have been sent unencrypted even when encrypted DNS was enabled. This...

In certain cases, SNI could have been sent unencrypted even when encrypted DNS was enabled. This vulnerability affects Firefox < 139.

Record: GHSA-hf6r-227w-qwf9
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness: CWE-319
Updated: 2026-11-02

NVD 7.5

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.

Record: CVE-2025-5270
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness: CWE-319
Updated: 2026-11-02

OSVUBUNTU-CVE-2025-5270 7.5

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.

Record: UBUNTU-CVE-2025-5270
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated: 2026-11-02

OSVopenSUSE-SU-2025:15196-1 No score

MozillaFirefox-139.0.1-1.1 on GA media

These are all security issues fixed in the MozillaFirefox-139.0.1-1.1 package on the GA media of openSUSE Tumbleweed.

Record: openSUSE-SU-2025:15196-1
Updated: 2026-11-02

OSVopenSUSE-SU-2026:11373-1 No score

firefox-esr-153.0-1.1 on GA media

These are all security issues fixed in the firefox-esr-153.0-1.1 package on the GA media of openSUSE Tumbleweed.

Record: openSUSE-SU-2026:11373-1
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`mozjs52` Ubuntu:18.04:LTS	All versions, plus listed versions 52.3.1-0ubuntu352.3.1-7fakesync152.8.1-0ubuntu0.18.04.152.9.1-0ubuntu0.18.04.1	None known
`mozjs38` Ubuntu:18.04:LTS	All versions, plus listed versions 38.8.0~repack1-0ubuntu138.8.0~repack1-0ubuntu338.8.0~repack1-0ubuntu4	None known
`mozjs68` Ubuntu:20.04:LTS	All versions, plus listed versions 68.5.0-1~fakesync68.5.0-2~fakesync68.6.0-168.6.0-1ubuntu1	None known
`mozjs52` Ubuntu:20.04:LTS	All versions, plus listed versions 52.9.1-1build152.9.1-1ubuntu3	None known
`mozjs102` Ubuntu:22.04:LTS	All versions, plus listed versions 102.11.0-0ubuntu0.22.04.1102.12.0-0ubuntu0.22.04.1102.13.0-0ubuntu0.22.04.1102.15.1-0ubuntu0.22.04.1	None known
`mozjs78` Ubuntu:22.04:LTS	All versions, plus listed versions 78.13.0-178.15.0-278.15.0-4ubuntu1	None known
`mozjs91` Ubuntu:22.04:LTS	All versions, plus listed versions 91.5.1-0ubuntu191.6.0-191.6.0-291.7.0-291.10.0-0ubuntu1	None known
`thunderbird` Ubuntu:22.04:LTS	before 1:140.7.1+build1-0ubuntu0.22.04.1, plus listed versions 1:91.1.2+build1-0ubuntu11:91.3.0+build2-0ubuntu11:91.3.1+build1-0ubuntu11:91.3.2+build1-0ubuntu11:91.4.0+build1.1-0ubuntu1 Show 33 moreShow less 1:91.4.0+build2-0ubuntu11:91.5.0+build1-0ubuntu11:91.5.1+build1-0ubuntu11:91.6.1+build1-0ubuntu11:91.7.0+build1-0ubuntu11:91.7.0+build2-0ubuntu11:91.8.0+build2-0ubuntu11:91.9.1+build1-0ubuntu0.22.04.11:91.11.0+build2-0ubuntu0.22.04.11:102.2.2+build1-0ubuntu0.22.04.11:102.4.2+build2-0ubuntu0.22.04.11:102.7.1+build2-0ubuntu0.22.04.11:102.8.0+build2-0ubuntu0.22.04.11:102.9.0+build1-0ubuntu0.22.04.11:102.10.0+build2-0ubuntu0.22.04.11:102.11.0+build1-0ubuntu0.22.04.11:102.13.0+build1-0ubuntu0.22.04.11:102.15.0+build1-0ubuntu0.22.04.11:102.15.1+build1-0ubuntu0.22.04.11:115.3.1+build1-0ubuntu0.22.04.21:115.4.1+build1-0ubuntu0.22.04.11:115.5.0+build1-0ubuntu0.22.04.11:115.6.0+build2-0ubuntu0.22.04.11:115.8.1+build1-0ubuntu0.22.04.11:115.9.0+build1-0ubuntu0.22.04.11:115.10.1+build1-0ubuntu0.22.04.11:115.11.0+build2-0ubuntu0.22.04.11:115.12.0+build3-0ubuntu0.22.04.11:115.13.0+build5-0ubuntu0.22.04.11:115.15.0+build1-0ubuntu0.22.04.11:115.16.0+build2-0ubuntu0.22.04.11:115.18.0+build1-0ubuntu0.22.04.11:128.12.0+build1-0ubuntu0.22.04.1	1:140.7.1+build1-0ubuntu0.22.04.1
`mozjs102` Ubuntu:24.04:LTS	All versions, plus listed versions 102.15.1-1102.15.1-3ubuntu2	None known
`mozjs115` Ubuntu:24.04:LTS	All versions, plus listed versions 115.3.0-0ubuntu1115.4.0-2115.5.0-1115.6.0-1115.7.0-4 Show 4 moreShow less 115.8.0-1115.9.0-1115.9.0-1build1115.10.0-1	None known
`MozillaFirefox` openSUSE:Tumbleweed From an advisory covering 9 CVEs	before 139.0.1-1.1	139.0.1-1.1
`firefox-esr` openSUSE:Tumbleweed From an advisory covering 228 CVEs	before 153.0-1.1	153.0-1.1

History

History
Recorded	Changed	Sources
Nov 6, 2026	affected, facts
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-5270 is a high vulnerability (CVSS 7.5) in Mozilla Firefox, published May 27, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.29%, the 21st percentile. Fixed in thunderbird 1:140.7.1+build1-0ubuntu0.22.04.1.

References

Show 194 moreShow less

This page doesn't list everything

Left out here: 43 references. The JSON record has them.