CVE-2026-74934

Analyzed Analyzed - Analysis Complete

Graphics: CanvasWebGL Site Isolation Flaw in Firefox

Publication date: 2026-08-18

Last updated on: 2026-08-24

Assigner: Mozilla Corporation

Description

Site isolation issue in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-08-18

Last Modified

2026-08-24

Generated

2026-09-08

AI Q&A

2026-08-18

EPSS Evaluated

2026-09-06

NVD

CVE-2026-74934

EUVD

EUVD-2026-60743

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 115.39.0 (exc)
mozilla	firefox	From 116.0 (inc) to 140.14.0 (exc)
mozilla	firefox	From 141.0 (inc) to 153.1.0 (exc)
mozilla	thunderbird	From 141.0 (inc) to 153.1.0 (exc)
mozilla	thunderbird	to 140.14.0 (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.
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.

Attack-Flow Graph

Executive Summary

This is a site isolation issue in Firefox's Graphics: CanvasWebGL component. Site isolation is a security feature that separates different websites into different processes to prevent data leaks between them. A flaw in CanvasWebGL could allow malicious websites to access data from other sites.

Detection Guidance

To detect this vulnerability, check the installed version of Firefox or Firefox ESR on your system. Compare it against the fixed versions: Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, or Firefox ESR 153.1. Use commands like 'firefox --version' or 'apt show firefox' depending on your OS.

Impact Analysis

If exploited, this vulnerability could allow an attacker to access sensitive data from other websites you have open in different tabs or windows. This might include personal information, login credentials, or other private data.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or other standards as it is a site isolation issue in Firefox's Graphics: CanvasWebGL component. No evidence suggests data exposure or privacy violations that would impact regulatory compliance.

Mitigation Strategies

Immediately update Firefox to version 154 or Firefox ESR to versions 115.39, 140.14, or 153.1. If automatic updates are disabled, manually download and install the latest version from Mozilla's official website.

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