CVE-2026-16387
Received Received - Intake

Firefox Networking Component Site Isolation Flaw

Publication date: 2026-07-21

Last updated on: 2026-07-21

Assigner: Mozilla Corporation

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

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Meta Information

Published
2026-07-21
Last Modified
2026-07-21
Generated
2026-07-21
AI Q&A
2026-07-21
EPSS Evaluated
N/A
NVD
CVE-2026-16387
EUVD
EUVD-2026-46224

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
mozilla firefox to 153 (inc)
mozilla firefox_esr to 140.13 (inc)
mozilla firefox 153
mozilla firefox_esr 140.13

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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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.

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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