CVE-2026-16399

Undergoing Analysis Undergoing Analysis - In Progress

Firefox DOM Navigation Site Isolation Flaw

Publication date: 2026-07-21

Last updated on: 2026-07-24

Assigner: Mozilla Corporation

Description

Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-07-21

Last Modified

2026-07-24

Generated

2026-08-11

AI Q&A

2026-07-21

EPSS Evaluated

2026-08-09

NVD

CVE-2026-16399

EUVD

EUVD-2026-46237

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	thunderbird	to 153.0 (exc)
mozilla	firefox	to 153.0.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-346	The product does not properly verify that the source of data or communication is valid.

Attack-Flow Graph

Executive Summary

This is a site isolation issue in Firefox's DOM Navigation component. It allows potential unauthorized access between different sites due to improper isolation of navigation actions.

Detection Guidance

This vulnerability is specific to Firefox versions before 153 and relates to a site isolation issue in the DOM Navigation component. Detection would require checking installed Firefox versions and monitoring for unusual navigation or DOM-related behaviors in web applications.

Impact Analysis

An attacker could exploit this to access data or perform actions on one site while you are logged into another site, potentially stealing sensitive information or hijacking sessions.

Compliance Impact

This vulnerability involves a site isolation issue in the DOM Navigation component, which could allow unauthorized access to sensitive data. For GDPR, this may impact data confidentiality and integrity requirements. For HIPAA, it could risk protected health information exposure. Organizations must assess if this flaw affects their data handling practices and implement mitigations like updating to Firefox 153.

Mitigation Strategies

Update Firefox to version 153 or later to address the site isolation issue in the DOM Navigation component.

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