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Mozilla Firefox EUVDEUVD-2026-69088

| CVE-2026-84140 CRITICAL
Origin Validation Error (CWE-346)
2026-09-01 mozilla GHSA-hg9w-cw2v-4pm9
Information Disclosure Mozilla Suse
9.8
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
6.9 MEDIUM

Browser origin-validation bug needs a victim to load malicious content (UI:R) and a crafted trigger (AC:H); crossing the site boundary is a scope change (S:C) yielding cross-origin disclosure (C:H) with minimal integrity and no availability impact.

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

Primary rating from NVD.

CVSS VectorNVD

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

Lifecycle Timeline

4
Analysis Generated
Sep 03, 2026 - 16:38 vuln.today
CVSS changed
Sep 03, 2026 - 16:37 NVD
9.8 (CRITICAL)
CVE Published
Sep 01, 2026 - 12:19 cve.org
UNKNOWN (no severity yet)
CVE Published
Sep 01, 2026 - 12:19 nvd
CRITICAL 9.8

DescriptionNVD

Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155 and Firefox ESR 153.2.

AnalysisAI

Cross-origin data exposure in Mozilla Firefox's DOM: Navigation component stems from a site isolation failure that lets malicious web content bypass the same-origin/site boundary Firefox enforces to keep pages from different sites in separate processes. The flaw affects Firefox before version 155 and Firefox ESR before 153.2, and could allow a crafted page to read or influence data belonging to another origin. …

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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 load attacker-controlled web content in an unpatched Firefox (before 155 / ESR before 153.2) and hinges on the specific DOM: Navigation site-isolation defect being triggered during a navigation. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The input CVSS is 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), but that rating is difficult to reconcile with the vulnerability class: a site-isolation/origin-validation flaw in a browser almost always requires a victim to visit or render attacker-controlled web content, which implies user interaction (UI:R) rather than UI:N, and its impact is weighted toward confidentiality (cross-origin data leakage) rather than full integrity and availability compromise. … 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 Firefox ESR 153.2 (or later); this is the primary and complete fix per Mozilla advisories MFSA2026-82/-85/-86/-88. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, inventory all Firefox and Firefox ESR deployments across your organization and notify end users of the critical security update requirement. …

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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 High Performance Computing 15 SP4-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Affected

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EUVD-2026-69088 vulnerability details – vuln.today
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