Improper privilege management in Mozilla products - CVE-2026-16365

Vulnerability identifier: #VU138995

CSH Severity: High

CVSS v4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-16365

CWE-ID: CWE-269

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to escalate privileges.

The vulnerability exists due to improper access control in the DOM: Workers component when handling worker operations. A remote attacker can trigger crafted worker behavior to escalate privileges.

Firefox ESR
Mozilla Firefox
Firefox for Android
Debian Linux
Mozilla Thunderbird
firefox-esr (Debian package)

Install security update from vendor's website.

Firefox ESR - addressed in versions 140.15.0, 153.2.0
Firefox for Android - update to 153.0
Mozilla Firefox - update to 153.0
Mozilla Thunderbird - update to 153.0
firefox-esr (Debian package) - update to 140.15.0esr-1~deb13u1

• https://www.mozilla.org/en-US/security/advisories/mfsa2026-68/
• https://bugzilla.mozilla.org/show_bug.cgi?id=2049149
• https://www.mozilla.org/en-US/security/advisories/mfsa2026-84/

• Multiple vulnerabilities in Mozilla Firefox
• Multiple vulnerabilities in Mozilla Thunderbird
• Debian update for firefox-esr