Name: CVE-2026-109739: Undefined Security Weakness
Creator: Rapid7
Published: 2026-10-13T00:00:00.000Z
License: https://www.rapid7.com/legal/website-terms-of-use/
Keywords: CVE, CVE-2026-109739, CWE-269, CVSS 8.8, EPSS 0.00157

Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 158 and Thunderbird 158.

CVSS Details

CVSS 3.1 Base Score: 8.8
CVSS 3.1 Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)

Covered by Rapid7

Product	Vendor Advisory	Solution File	Added	Published
Mfsa2026 106	—	Upgrade to Mozilla Firefox version 158.0Upgrade to the latest version of Mozilla Firefox	Oct 13, 2026	Oct 13, 2026
Mozilla Thunderbird	—	Upgrade to the latest version of Mozilla ThunderbirdUpgrade to Mozilla Thunderbird version 158.0	Oct 13, 2026	Oct 13, 2026

Prioritise with Active Threat Intelligence

With curated Threat Intelligence, you can see which vulnerabilities truly put you at risk, prioritize what matters most, and act before attackers do.

Explore Intelligence Hub

MDR Buyer's Guide

Global Threat Landscape Report

Grow your business

CVSS Details

Covered by Rapid7

Prioritise with Active Threat Intelligence