CVE-2026-16365 is a privilege escalation vulnerability affecting the DOM: Workers component in Mozilla Firefox. It allows an attacker to gain elevated privileges within the browser context. The vulnerability was reported by Khanh Nguyen and is classified under CWE-269 (Improper Privilege Management) and CWE-284 (Improper Access Control). Mozilla fixed this issue in Firefox 153 and Thunderbird 153 as part of a security advisory (MFSA 2026-68 and MFSA 2026-71) that addressed multiple high-impact vulnerabilities. The CVSS v3.1 base score is 8.8, indicating a high severity with network attack vector, low attack complexity, no privileges required, user interaction required, and high impact on confidentiality, integrity, and availability.

Successful exploitation of this vulnerability could allow an attacker to escalate privileges within the Firefox browser environment, potentially leading to unauthorized access to sensitive information, modification of data, or disruption of service. The vulnerability affects the security boundary of the DOM Workers component, which could be leveraged to bypass normal privilege restrictions. However, there are no known exploits in the wild at the time of this advisory.

Mozilla has released an official fix for this vulnerability in Firefox 153 and Thunderbird 153. Users and administrators should update affected products to version 153 or later to remediate this issue. Since this is a client-side vulnerability, applying the official update is the recommended and effective mitigation. No additional actions are required beyond applying the update.