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Mozilla Firefox CVE-2026-84133

| EUVDEUVD-2026-69081 CRITICAL
Origin Validation Error (CWE-346)
2026-09-01 mozilla GHSA-6932-cxg9-jprv
Information Disclosure Mozilla Suse
9.8
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) PRIMARY
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
6.5 MEDIUM

Browser cross-origin leak requires the victim to load malicious web content (UI:R) and yields confidentiality-only impact, so I:N/A:N and no privileges needed.

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

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

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 - 20:39 vuln.today
CVSS changed
Sep 03, 2026 - 18:37 NVD
9.8 (CRITICAL)
CVE Published
Sep 01, 2026 - 12:18 cve.org
CRITICAL 9.8
CVE Published
Sep 01, 2026 - 12:18 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

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

AnalysisAI

Cross-origin information disclosure in Mozilla Firefox arises from a site-isolation failure in the DOM Push Subscriptions component (CWE-346, origin validation error), allowing content from one origin to be improperly associated with or exposed to another. It affects Firefox before 155 and Firefox ESR before 153.2, and was disclosed and patched by Mozilla; there is no public exploit identified at time of analysis and EPSS is very low (0.14%, 4th percentile). …

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Attack ChainAIDerived

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Vulnerability AssessmentAI

Exploitation Exploitation requires the victim to visit or render attacker-controlled web content in an unpatched Firefox (before 155) or Firefox ESR (before 153.2) that exercises the DOM Push Subscriptions path; the abused feature is the Web Push subscription mechanism, so environments with push notifications disabled are less exposed. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The vendor CVSS of 9.8 (AV:N/AC:L/PR:N/UI:N/C:H/I:H/A:H) overstates this for a browser cross-origin issue: an origin-validation/site-isolation bug of this class almost always requires the victim to load attacker-controlled web content (UI:R, not UI:N) and yields a confidentiality leak, not full integrity/availability compromise - so I:H/A:H are not supported by the description. … 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, per Mozilla advisories mfsa2026-86/mfsa2026-88 (https://www.mozilla.org/security/advisories/mfsa2026-86/). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, communicate to all Firefox users and system administrators about the availability of Firefox 155 and Firefox ESR 153.2, including a clear upgrade timeline. …

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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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CVE-2026-84133 vulnerability details – vuln.today
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