CVE-2026-84121

CriticalCVSS 9.6/10Last modified Sep 2, 2026

Description

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.

Metrics

CVSS 3.1 9.6/10CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Weakness enumeration

CWE-416

Affected software

No affected versions have been published.

Timeline

Published
Sep 1, 2026
Last modified
Sep 2, 2026
NVD status
Analyzed

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CVE-2026-84121: Critical severity, CVSS 9.6 | Vulnix