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Mozilla Firefox CVE-2026-74939

| EUVDEUVD-2026-60746 HIGH
Improper Privilege Management (CWE-269)
2026-08-18 mozilla GHSA-mcwh-jxcv-xq9h
Privilege Escalation Red Hat Mozilla Suse
8.8
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) PRIMARY
8.8 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
vuln.today AI
8.8 HIGH

Network-delivered via webpage visit with UI:R for page navigation; S:U as privilege escalation stays within Firefox process, not OS; PR:N confirmed by lack of any authentication precondition.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
SUSE
HIGH
qualitative
Red Hat
7.5 HIGH
qualitative

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

4
Analysis Generated
Aug 18, 2026 - 16:29 vuln.today
CVSS changed
Aug 18, 2026 - 16:22 NVD
8.8 (HIGH)
CVE Published
Aug 18, 2026 - 12:23 cve.org
UNKNOWN (no severity yet)
CVE Published
Aug 18, 2026 - 12:23 cve.org
HIGH 8.8

DescriptionCVE.org

Privilege escalation in the DOM: Navigation component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1.

Articles & Coverage 1

News 12 New Mozilla Vulnerabilities - 12 High Severity, No POC Available Aug 18, 2026

AnalysisAI

Privilege escalation in Firefox's DOM Navigation component allows a remote unauthenticated attacker to achieve full confidentiality, integrity, and availability compromise within the browser process by inducing a user to visit a malicious webpage. All Firefox releases prior to version 154 and all active ESR branches (115.x, 140.x, 153.x) are affected, with Mozilla issuing four simultaneous MFSA advisories (mfsa2026-74 through mfsa2026-77) indicating broad impact across every supported release channel. No public exploit or KEV listing has been identified at time of analysis, but the low attack complexity and zero authentication requirement make this a high-priority patch for all Firefox deployments.

Technical ContextAI

The vulnerability resides in Firefox's DOM Navigation component (CWE-269: Improper Privilege Management), which manages browser navigation events, history traversal, and document loading sequences. CWE-269 indicates that privilege boundaries between web content and the browser's internal privilege layers are not properly enforced during navigation operations, potentially allowing script or page-level content to assume elevated permissions within the browser process. The affected codebase covers all Mozilla Firefox application builds per CPE cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*, encompassing standard release, Extended Support Release (ESR) 115.x, ESR 140.x, and ESR 153.x channels. The simultaneous publication of four MFSA advisories suggests the flaw manifests across diverged ESR codebases rather than being confined to a single code path.

RemediationAI

The primary remediation is to upgrade Firefox immediately: standard release users should update to Firefox 154 or later; ESR 115.x users to Firefox ESR 115.39; ESR 140.x users to Firefox ESR 140.14; ESR 153.x users to Firefox ESR 153.1. All four patched versions are confirmed by Mozilla's advisory set (mfsa2026-74 through mfsa2026-77) at https://www.mozilla.org/security/advisories/. Enterprise deployments managed via Group Policy or Mozilla Enterprise Policies should push the update through their software distribution channel immediately. If immediate patching is operationally blocked, a compensating control is to restrict or block access to untrusted external web content using a web proxy or DNS filtering appliance, which reduces exposure to attacker-controlled pages - note this does not eliminate risk from compromised trusted sites. Disabling JavaScript via browser policy (javascript.enabled=false) would remove the attack surface but severely impairs browser functionality and is not viable for general-purpose use.

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Same weakness CWE-269 – Improper Privilege Management

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Same technique Privilege Escalation

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
Container suse/kiosk/firefox-esr:140.14-75.12 Affected
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise High Performance Computing 15 SP7 SUSE Linux Enterprise Module for Desktop Applications 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Fixed

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CVE-2026-74939 vulnerability details – vuln.today
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