CVE-2026-74981

Analyzed Analyzed - Analysis Complete

Site Isolation Bypass in Firefox Web Codecs

Publication date: 2026-08-18

Last updated on: 2026-08-25

Assigner: Mozilla Corporation

Description

Site isolation issue in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-18

Last Modified

2026-08-25

Generated

2026-09-07

AI Q&A

2026-08-18

EPSS Evaluated

2026-09-06

NVD

CVE-2026-74981

EUVD

EUVD-2026-60694

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 153.1.0 (exc)
mozilla	thunderbird	to 153.1.0 (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 Audio/Video: Web Codecs component. Site isolation is a security feature that separates content from different websites to prevent data leaks. A flaw in this component could allow malicious websites to access data from other sites.

Detection Guidance

This vulnerability is specific to Firefox versions before 154 and Firefox ESR before 153.1. To detect it, check your installed Firefox version by running 'firefox --version' or 'about:support' in Firefox. If your version is below 154 (or 153.1 for ESR), your system is vulnerable.

Impact Analysis

If exploited, this vulnerability could allow an attacker to access sensitive data from other websites you visit while using Firefox. This might include login credentials, personal information, or other confidential data.

Compliance Impact

This vulnerability could lead to unauthorized data access, potentially violating privacy regulations like GDPR or HIPAA if sensitive personal or health data is exposed. Organizations must ensure patches are applied to maintain compliance.

Mitigation Strategies

Update Firefox to version 154 or later and Firefox ESR to version 153.1 or later to address the Site isolation issue in the Audio/Video: Web Codecs component.

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