Vulnerability · NVD

CVE-2026-84121

CVE-2026-84121, critical severity (CVSS 9.6): 2 tracked apps concerned, 1 still exposed on its current version.

Severity (CVSS): 9.6
Exploitation: -
Tracked apps: 2
Still exposed: 1

Published on 2026-09-01

Sandbox escape due to use-after-free in the DOM: Security component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

Attack vector : Network No privileges required

Show raw CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Tracked apps referencing this CVE

For each app: the affected range, the fixing version, and where the tracked app stands today.

Mozilla Firefox Windows winget:Mozilla.Firefox

Affected <115.40.0 Fixed in 115.40.0 Latest tracked 155.0 patched

Observed affected builds (57)

115.0.3 115.0.2 115.0.1 115.0 114.0.2 114.0.1 113.0.2 113.0.1 113.0 112.0.2 112.0.1 112.0 111.0.1 111.0 110.0.1 110.0 109.0.1 109.0 108.0.2 108.0.1 108.0 107.0.1 107.0 106.0.5 106.0.4 106.0.3 106.0.2 106.0.1 106.0 105.0.3 +27 · see history
Mozilla Thunderbird Windows winget:Mozilla.Thunderbird

Affected ≥154.0 <155.0 Fixed in 155.0 Latest tracked 154.0 still vulnerable

Observed affected builds (1)

154.0

Vulnerable CPE configurations (7)

Vendor	Product	Platform	Versions	CPE 2.3 URI
mozilla	firefox All platforms (wildcard)	All platforms (wildcard)	<115.40.0	cpe:2.3:a:mozilla:firefox::::::::
mozilla	firefox All platforms (wildcard)	All platforms (wildcard)	≥116.0 <140.15.0	cpe:2.3:a:mozilla:firefox::::::::
mozilla	firefox All platforms (wildcard)	All platforms (wildcard)	≥141.0.0 <153.2.0	cpe:2.3:a:mozilla:firefox::::::::
mozilla	firefox All platforms (wildcard)	All platforms (wildcard)	≥154.0.0 <155.0.0	cpe:2.3:a:mozilla:firefox::::::::
mozilla	thunderbird All platforms (wildcard)	All platforms (wildcard)	<140.15.0	cpe:2.3:a:mozilla:thunderbird::::::::
mozilla	thunderbird All platforms (wildcard)	All platforms (wildcard)	≥141.0 <153.2.0	cpe:2.3:a:mozilla:thunderbird::::::::
mozilla	thunderbird All platforms (wildcard)	All platforms (wildcard)	≥154.0 <155.0	cpe:2.3:a:mozilla:thunderbird::::::::

View on NVD ↗ Advisory · www.mozilla.org