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Mozilla Firefox ESR < 140.15

critical Nessus Plugin ID 342131

Synopsis

A web browser installed on the remote Windows host is affected by multiple vulnerabilities.

Description

The version of Firefox ESR installed on the remote Windows host is prior to 140.15. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-84 advisory.

 - Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154 and Thunderbird 154. (CVE-2026-75874)

 - Privilege escalation in the DOM: Workers component. This vulnerability was fixed in Firefox 153, Thunderbird 153, and Firefox ESR 140.15. (CVE-2026-16365)

 - Use-after-free in the Audio/Video component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, and Firefox ESR 153.2. (CVE-2026-84120)

 - Use-after-free in the Audio/Video component. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, and Firefox ESR 153.2. (CVE-2026-84122)

 - Privilege escalation in the DOM: Navigation component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, Thunderbird 140.13, and Firefox ESR 140.15. (CVE-2026-16371)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Upgrade to Mozilla Firefox ESR version 140.15 or later.

See Also

https://www.mozilla.org/en-US/security/advisories/mfsa2026-84/

Plugin Details

Severity: Critical

ID: 342131

File Name: mozilla_firefox_140_15_esr.nasl

Version: 1.1

Type: Local

Agent: windows

Family: Windows

Published: 9/1/2026

Updated: 9/1/2026

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 5

Percentile: 93.74

CVSS v2

Risk Factor: Critical

Base Score: 10

Temporal Score: 7.4

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C

CVSS Score Source: CVE-2026-75874

CVSS v3

Risk Factor: Critical

Base Score: 10

Temporal Score: 8.7

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:mozilla:firefox_esr

Required KB Items: installed_sw/Mozilla Firefox ESR

Exploit Ease: No known exploits are available

Patch Publication Date: 9/1/2026

Vulnerability Publication Date: 7/21/2026

Reference Information

CVE: CVE-2026-16365, CVE-2026-16371, CVE-2026-75874, CVE-2026-84119, CVE-2026-84120, CVE-2026-84121, CVE-2026-84122, CVE-2026-84124, CVE-2026-84131, CVE-2026-84143, CVE-2026-84145

IAVA: 2026-A-0755-S, 2026-A-0876