CVE-2026-84137

Modified Modified - Updated After Analysis

DOM Spoofing in Firefox 155 and Firefox ESR 153.2

Publication date: 2026-09-01

Last updated on: 2026-09-03

Assigner: Mozilla Corporation

Description

Spoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-01

Last Modified

2026-09-03

Generated

2026-09-21

AI Q&A

2026-09-01

EPSS Evaluated

2026-09-20

NVD

CVE-2026-84137

EUVD

EUVD-2026-69085

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 153.2.0 (exc)
mozilla	firefox	From 154.0.0 (inc) to 155.0.0 (exc)
mozilla	thunderbird	to 153.2.0 (exc)
mozilla	thunderbird	From 154.0 (inc) to 155.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-451	The user interface (UI) does not properly represent critical information to the user, allowing the information - or its source - to be obscured or spoofed. This is often a component in phishing attacks.
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 spoofing vulnerability in the DOM Core and HTML components of Firefox. It allows an attacker to deceive users by manipulating the appearance of web content, potentially leading them to interact with malicious or fake elements.

Detection Guidance

Detection requires checking Firefox and Firefox ESR versions. If your system runs Firefox <155 or Firefox ESR <153.2, it is vulnerable. Use commands like 'firefox --version' or 'apt show firefox' to check versions.

Impact Analysis

An attacker could exploit this to trick you into revealing sensitive information, downloading malware, or performing unintended actions by making malicious content appear legitimate in your browser.

Compliance Impact

The provided CVE data does not specify how this vulnerability affects compliance with standards like GDPR or HIPAA. The description only mentions a spoofing issue in Firefox components without details on potential data exposure or privacy impacts.

Mitigation Strategies

Update Firefox to version 155 or later and Firefox ESR to version 153.2 or later to address the spoofing vulnerability in the DOM: Core & HTML component.

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