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Mozilla Firefox CVE-2026-84119

| EUVDEUVD-2026-69064 CRITICAL
Use After Free (CWE-416)
2026-09-01 mozilla GHSA-jm34-3r5q-pm6j
Information Disclosure Memory Corruption Use After Free Mozilla Suse
9.6
CVSS 3.1 · Vendor: mozilla
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Severity by source

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

Network-reachable via a visited page (UI:R, PR:N) with sandbox scope change and full host impact; AC:H reflects heap-grooming needed to reliably exploit a UAF sandbox escape.

3.1 AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H
4.0 AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
SUSE
8.3 HIGH
AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

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

Lifecycle Timeline

4
Analysis Generated
Sep 01, 2026 - 15:41 vuln.today
CVSS changed
Sep 01, 2026 - 15:22 NVD
9.6 (CRITICAL)
CVE Published
Sep 01, 2026 - 12:18 cve.org
UNKNOWN (no severity yet)
CVE Published
Sep 01, 2026 - 12:18 cve.org
CRITICAL 9.6

DescriptionCVE.org

Sandbox escape due to use-after-free in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, and Firefox ESR 153.2.

Articles & Coverage 2

News 7 New Mozilla Vulnerabilities - 2 Critical, 5 High Severity Sep 02, 2026 News Critical Sandbox Escape via Use-After-Free in Mozilla Firefox - CVE-2026-84119 Sep 01, 2026

AnalysisAI

Sandbox escape in Mozilla Firefox stems from a use-after-free in the DOM: Navigation component, letting a malicious web page that a user visits corrupt memory and potentially execute code outside the content sandbox. It affects Firefox before 155 and multiple ESR trains (115.x, 140.x, 153.x), carries a critical 9.6 CVSS with a scope change (browser sandbox to host), and requires the victim to load attacker-controlled content (UI:R). …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Exploitation requires the victim to actively load attacker-controlled web content in Firefox (CVSS UI:R) that triggers the specific navigation sequence freeing and reusing a DOM Navigation object; no authentication or elevated privileges are needed (PR:N). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H = 9.6 critical) signals a remotely reachable, low-complexity, unauthenticated bug whose only gate is user interaction (visiting a page) and whose sandbox escape yields total host impact - consistent with SSVC Technical Impact: total. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Vendor-released patch: upgrade to Firefox 155 or, for extended-support deployments, Firefox ESR 115.40, ESR 140.15, or ESR 153.2 as applicable to your channel. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours: Issue urgent advisory instructing users to restrict Firefox usage to trusted sites or switch to alternative browsers for general web browsing; inventory business-critical systems dependent on Firefox. …

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Same weakness CWE-416 – Use After Free

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Same technique Information Disclosure

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Module for Desktop Applications 15 SP7 Affected
SUSE Linux Enterprise Module for Package Hub 15 SP7 Affected

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CVE-2026-84119 vulnerability details – vuln.today
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