CVE-2026-8971

Analyzed Analyzed - Analysis Complete

Same-origin policy bypass in Firefox

Publication date: 2026-05-19

Last updated on: 2026-05-20

Assigner: Mozilla Corporation

Description

Same-origin policy bypass in the Networking: JAR component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-05-19

Last Modified

2026-05-20

Generated

2026-06-30

AI Q&A

2026-05-19

EPSS Evaluated

2026-06-28

NVD

CVE-2026-8971

EUVD

EUVD-2026-30919

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 151.0.0 (exc)
mozilla	thunderbird	to 151.0.0 (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 vulnerability is a same-origin policy bypass in the Networking: JAR component of Firefox. The same-origin policy is a security measure that restricts how documents or scripts loaded from one origin can interact with resources from another origin. A bypass means that this restriction can be circumvented, potentially allowing unauthorized access to data or functionality across different origins. This issue was fixed in Firefox version 151.

Impact Analysis

By bypassing the same-origin policy in the JAR networking component, an attacker could potentially access or manipulate data from other origins without proper authorization. This could lead to unauthorized data exposure, cross-site scripting, or other security breaches when using affected versions of Firefox prior to version 151.

Mitigation Strategies

To mitigate this vulnerability, update Firefox to version 151 or later where the issue has been fixed.

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