Vulnerability · NVD

CVE-2026-74986

CVE-2026-74986, critical severity (CVSS 9.1): 1 tracked app concerned, all fixed or indeterminable on their current version.

Severity (CVSS): 9.1
Exploitation: 0.3 %
Tracked apps: 1
Still exposed: 0

Published on 2026-08-18

Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.

Attack vector : Network No privileges required No user interaction

Show raw CVSS vector

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

EPSS 0.34% exploit very unlikely percentile 26.9%

Tracked apps referencing this CVE

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

Mozilla Thunderbird Windows winget:Mozilla.Thunderbird

Affected <153.1.0 Fixed in 153.1.0 Latest tracked 154.0 patched

Observed affected builds (128)

153.0.3 153.0.2 153.0.1 153.0 152.0.1 152.0 151.0.1 151.0 150.0.2 150.0.1 150.0 149.0.2 149.0.1 149.0 148.0.1 148.0 147.0.2 147.0.1 147.0 146.0.1 146.0 145.0 144.0.1 144.0 143.0.1 143.0 142.0 141.0 140.0.1 140.0 +98 · see history

Vulnerable CPE configurations (1)

Vendor	Product	Platform	Versions	CPE 2.3 URI
mozilla	thunderbird All platforms (wildcard)	All platforms (wildcard)	<153.1.0	cpe:2.3:a:mozilla:thunderbird::::::::

View on NVD ↗ Advisory · www.mozilla.org