CVE-2026-16387

Analyzed Analyzed - Analysis Complete

Firefox Networking Component Site Isolation Flaw

Publication date: 2026-07-21

Last updated on: 2026-07-24

Assigner: Mozilla Corporation

Description

Site isolation issue in the Networking component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-07-21

Last Modified

2026-07-24

Generated

2026-08-10

AI Q&A

2026-07-21

EPSS Evaluated

2026-08-09

NVD

CVE-2026-16387

EUVD

EUVD-2026-46224

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 153.0.0 (exc)
mozilla	firefox	to 140.13.0 (exc)
mozilla	thunderbird	to 140.13.0 (exc)
mozilla	thunderbird	From 141.0 (inc) to 153.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-200	The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
CWE-284	The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
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 Networking component. Site isolation is a security feature that separates content from different websites to prevent malicious sites from accessing data on other sites. A flaw in this component could allow unauthorized access between sites.

Detection Guidance

This vulnerability is a site isolation issue in Firefox's Networking component, fixed in Firefox 153 and Firefox ESR 140.13. Detection requires checking Firefox version against these updates. Use commands like 'firefox --version' or 'about:support' in Firefox to verify installed version.

Impact Analysis

An attacker could exploit this to access sensitive data from other websites you visit while using Firefox. This might include cookies, login credentials, or other personal information if you have multiple tabs open.

Compliance Impact

The provided CVE data does not specify how this vulnerability impacts compliance with standards like GDPR or HIPAA. The description only mentions a site isolation issue in Firefox's Networking component, fixed in versions 153 and ESR 140.13.

Mitigation Strategies

Update Firefox to version 153 or later and Firefox ESR to version 140.13 or later to address the site isolation issue in the Networking component.

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