CVE-2026-84129 | BDVDB-2026-367104 Detail

MozillaFirefox

Description#

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

Impact#

Per CVSS v3.1: confidentiality impact high, integrity impact high, availability impact high. Attack vector: network.

Weaknesses#

CWE-346 Origin Validation Error

References#

Exploit#

No public exploit known

History#

Version 12026-09-01Record published in the CVE List.
Version 22026-09-02Most recent update recorded in the CVE List.

Published

Published: 2026-09-01
Last modified: 2026-09-02

Vendor information

Vendor: Mozilla
Product: Firefox

All Mozilla vulnerabilities

Score

9.8 Critical

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 8.2.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Not classified

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
Not stated
Fixed
153.2
Vulnerable
Not stated
Fixed
155

Scoring System

CVSS v4.0

Not available

CVSS v3.1

9.8 Critical

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).