--- title: "CVE-2026-109739: Firefox - Privilege Escalation" description: "Firefox contains a privilege escalation vulnerability in the WebExtensions component, letting attackers escalate their privileges, exploit requires unspecified conditions." url: https://panop.io/threat-heartbeat/CVE-2026-109739/ --- # CVE-2026-109739 Firefox - Privilege Escalation Firefox contains a privilege escalation vulnerability in the WebExtensions component, letting attackers escalate their privileges, exploit requires unspecified conditions. CVSS base score 8.8 /10 High CISA KEV Not listed Public exploit None known EPSS 0.16% chance of exploitation in 30 days [View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-109739) ## Details Type Privilege Escalation Impact Privilege Escalation CVSS vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Published 13 October 2026 Updated 15 October 2026 Weakness [CWE-269](https://cwe.mitre.org/data/definitions/269.html) ## Vendor fix Update to Firefox 158 or later. Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them. ## References - [https://nvd.nist.gov/vuln/detail/CVE-2026-109739](https://nvd.nist.gov/vuln/detail/CVE-2026-109739) - [https://www.mozilla.org/security/advisories/mfsa2026-109/](https://www.mozilla.org/security/advisories/mfsa2026-109/) - [https://bugzilla.mozilla.org/show\_bug.cgi?id=2049069](https://bugzilla.mozilla.org/show_bug.cgi?id=2049069) - [https://www.mozilla.org/security/advisories/mfsa2026-106/](https://www.mozilla.org/security/advisories/mfsa2026-106/) [← All CVEs](https://panop.io/threat-heartbeat/) ## What this record can't tell you - Whether you run the affected software, and where - Whether an attacker can actually reach and exploit it - The misconfigurations that never get a CVE number - What it would cost the business, ranked into what to fix first Panop answers these inside your environment, for this CVE and every other finding. [Book a demo](https://panop.io/demo)